TIEZU, CHINA -- Zhao Chunlan, a 73-year-old widow, knows she can count on her son to look after her in her old age.

It is not just the notion of filial piety that is putting Zhao's mind at ease; her 51-year-old son and daughter-in-law have signed a support agreement to provide for her material and mental well-being.

In the agreement, the couple has promised to cook her special meals and take her for regular medical checkups. They also agreed to give her the largest room in the house, put the family's color television in her room and "never make her angry." Zhao acknowledges that her son took good care of her even before the agreement, "but now that he's signed it, he will be more conscious of his commitment," she said with a smile.

Such support agreements between children and their elderly parents, which are starting to be required in some localities by officials attempting to protect the aged, are a new phenomenon in a country that for thousands of years prided itself on reverence for age. Together with rising incidences of abuse and neglect of the aged in recent years, the agreements reflect the growing social problem posed by the country's rapidly increasing elderly population.

Because of a longer life expectancy and the implementation more than a decade ago of a birth control policy that permitted families to have only one child, China's over-60 population has increased much faster than the overall population.

According to Western estimates, about 65 million people, or 6 percent of China's population, are over 65. If the one-child policy is maintained successfully, which is not certain, the figure is likely to mushroom to 41 to 45 percent of the overall population by the middle of the 21st century, leaving far fewer of the able-bodied to care for elderly relatives.

"The trend of the future will be what we call the ratio of 4:2:1," said Song Yuhua, an official of China's National Committee on Aging, which oversees affairs of the elderly. "That means one child will have to take care of two parents and four grandparents, and this could result in a series of problems."

Western demographers note that no country has yet had more than 18 percent of its population in the 65-and-older category. With many developed countries already straining to care for their elderly, "the prospect of an elderly population comprising 30 to 45 percent of China's total population is daunting," said Judith Banister, a demographer at the U.S. Census Bureau, in a report on China's aging population.

Some Chinese planners, partly as a result of the aging problem, are now suggesting that the controversial one-child policy be modified to allow families to have two children by the end of the century.

The economic reforms of the past decade have also contributed to new social problems for the elderly. Communes, which carried out important welfare functions, were dismantled in the late 1970s, and the return of private initiative has left local authorities with far less power than before to become involved in the affairs of families. Those trends, together with the lack of a national social security system, have made the elderly even more dependent on family financial support, according to Chinese and Western experts.

In some cases, the burden has led to severe mistreatment of the elderly, according to Chinese officials and reports in the state press. Some elderly have had their money misappropriated, been denied food and medicine, and been beaten. Some have committed suicide.

In one case in Zhejiang province, an 81-year-old woman was scolded and beaten by her son and daughter-in-law, driven out of their home and forced to become a beggar, according to a report this summer in the official Legal Daily newspaper.

She sued her son, and a court ordered that 45 yuan, or about $9, be deducted from his factory wages each month to support his mother. But her son and daughter-in-law assaulted her for refusing to return the benefits, and the woman died within a few months. Police detained the son but released him a few days later.

"What requires our attention is that these cases have not aroused enough attention from the local legal authorities, and this situation has encouraged the bad trend of mistreating the elderly," the newspaper said.

Moreover, the newspaper said, the incident was not an isolated case. In a partial survey of 37 cities and counties in Zhejiang province alone, 187 elderly Chinese have died "abnormal deaths" since 1988 as a result of being denied medical treatment, being coerced into turning over property and being bullied and tortured. These deaths included suicide by poisoning, hanging, jumping from tall buildings and drowning.

"China has a long tradition of respect for the elderly, but as a result of the economic development, we are beginning to see individual instances of neglect of the elderly," said Yuan Xinli, an official with China's National Committee on Aging. The committee has no statistics on the number of abuse cases, but he said, "this is a very serious problem."

The loosening of controls that came with the economic reforms "made it easy for people to think only of their private ends," he said, "so it was easy for the elderly to become neglected."

China's marriage law includes provisions for the care of the elderly, but authorities say the elderly need more protection. Authorities are currently drafting a national law that would include specific measures such as guaranteeing the elderly the right to enjoy the same standard of living as their children, Yuan said.

Financial support for China's elderly depends almost completely on their families, except for a pension program that benefits part of the urban population. The retirement system applies only to employees of the state, workers in state-owned enterprises and workers in large urban collective enterprises.

Western and Chinese experts on aging say it is unlikely that China will develop a national pension or social security system in the near future. According to the latest figures, only about 22 million people received some sort of retirement benefits in 1988.

In the countryside, where most of China's 1.1 billion people live, most rural workers have no retirement system, and the government expects sons and their spouses and children to provide financial support and all necessary care for their aged parents.

To help protect the rights of the elderly, particularly in rural areas, some localities have begun requiring contracts of support between elderly parents and their children. A case in point is the village of Tiezu, or Iron Mouth in English, located in Qindu county on the outskirts of Xianyang, a former ancient capital of China in central Shaanxi province.

Starting this year, newlyweds in Qindu district have been required to sign contracts pledging to support their parents after age 60. Older, more-established married couples have been required to sign much more detailed agreements.

"The aim of the agreements is to prevent the rejecting of old parents, to prevent children from cutting off their responsibility of supporting their parents," said Shi Quanji, vice chairman of the county's committee on aging. With an elderly population of 27,200, an estimated 4,000 couples have so far signed some kind of support agreement, he said.

Although cases of abuse have been rare here in Tiezu, he said, it is very common for children, particularly sons, who are the traditional care-providers, to quarrel among themselves about who will take care of the parent.

The agreements, enforced by the aging committee, try to prevent such quarrels by laying out each child's responsibilities as clearly as possible. In the case of Zhao Jianfang and his wife, for example, their eldest son, Zhao Xiaobao, has agreed to provide the material for his parents' clothes, shoes and socks, while their younger son, Zhao Erbao, will be responsible for making the clothes.