Just a few years after kissing in public was scorned as bourgeois decadence, Chinese are furiously leafing through a new, officially authorized sex manual so popuolar that it is being sold openly at scalpers' prices.

The pocket-sized pamphlet boldly titled "Sexual Knowledge" purports to strip away the mystery and superstition shrouding lovemaking -- in line with the current official policy of facing up to reality.

To the Western eye, however, the authors' didactic tone and curious omission of such details as how intercourse is actually performed make the booklet read more like, in the words of one observer, "everything the party wants you to know about sex."

Masters and Johnson, in fact, might even question whether China's efforts to modernize have as yet reached the bedroom.

In a nation that espouses socialist solidarity, the Communist Party takes an uncompromising stand against sexual self-gratification. Masturbation, literally translated as "hand lewdness," is said to detract from one's work and study and ultimately cause impotence and "severe nervous disorder."

As a remedy for such indulgence, the two prestigious prefessors who authorized the 74-page study recommend a variety of measures including washing the feet with warm water before bedtime, staying away from tight-fitting trousers and heavy blankets and, of course, upholding "responsibility for your country and the socialist system."

Little heed is paid to what is popularly known in the West as female sexual equality. One passage concludes that the "male sex urge is often stronger than the female's" and points out that women require a certain amount of verbal romancing before really appreciating the sex act.

As an exception, Chinese readers are informed of the unfortunate case of a female artist who married a violinist 10 years her senior. Her sex drive was too strong for her husband to contain, the guidebook explains, so she requested an operation to lessen her urge.

While obviously old-fashioned by Western standards, "Sexual Knowledge" represents a real breakthrough in one of the world's most puritanical nations. The 2.5 million copies published in June sold out almost immediately at about 15 cents each. Copies have since been resold for almost double the price in front of Peking's Gate of Heavenly Peace.

The precious magenta treatise is actually a revised, expanded version of a 1957 manual, which disappeared during the book-burning days of the Cultural Revolution in the late 1960s and became forbidden fruit in the mid-1970s when the so-called Gang of Four radicals strongly condemned such innocent acts as holding hands among couples and wearing makeup among women.

For most Chinese, even a dry and limited analysis opens the door to the mysterious world of sex. Chinese society is virtually asexual, with none of the suggestive movies, books, clothing and advertisements so prevalent in the West.

Although China's dynastic history spins out stories of the emperors' concubines and the more recent fathers of the Communist revolution are said to have enjoyed an active sex life in their mountain redoubt, sex remains a taboo subject today.

Parents regard sexual instruction for their children as embarrassing, and schools provide little if any sex education. Chinese doctors, aware of the reluctance of many patients to reveal sexual disorders, are said to ask them euphemistically if they kidneys hurt.

Premarital sex has become a bit more common in recent years, according to Chinese youth, although it is generally a prelude to marriage and rarely indulged in as a simple pleasure. Officially, the government frowns on such practice.

It is in this most populous and sexually innocent nation that the new manual enters, hoping, in the words of its authors, to increase general knowledge so that Chinese "can have a sounder body and mind."

With diagrams and arrows, it methodically describes the male and female sexual organs and provides a long account of the reproduction of plants and single-cell organisms.

Another diagram describes the "five stages of breast growth" with a caveat that the final phase only occurs after marriage. Terms such as foreplay and erogenous zones, which appear like landmarks in sexual manuals of the West, are conspicuously absent in "Sexual Knowledge" as are the usual step-by-step exercises leading up to coitus.

China's new sex pathfinders are less timid about prescribing how often intercourse should be performed and the best time of day for it. Nighttime, readers are told, provides the most favorable hours for sex because it allows for the necessary rest "to repair strength."

On sexual frequency, the pamphlet advices, newlyweds will have "very, very frequent sex right after marriage: that is, once every three to seven days." As passions cool, it says, married couples can expect a more normal routine of "once every one or two weeks."

But the guidebook defers to individual taste in this matter, suggesting that sexual activity "should depend on how the couple feels the morning after they have sex.

"When the frequency is balanced, they will not feel tired the day after. In fact, quite the opposite, their whole body is light and loose and relaxed, and their temperament is happy."

A sure sign of overindulgence, the professors stress, is if the sexual partners "feel tired, heavy-headed, if their legs are tingly and ticklish, if their heart beats rapidly and they're short of breath or lose their appetite."