Early in the morning of April 24, police broke down the door of Jaroslaw Kozinski's apartment, conducted a search, and discovered about 200 clandestinely printed books and newspapers. Kozinski was arrested and quickly ordered before a judge under Poland's summary trial procedure.

By the next afternoon, Kozinski, a 34-year-old physicist, had been convicted of "spreading social disorder" and already had started serving a sentence of one year in jail. Three witnesses had testified against him, all of them police. They accused Kozinski of belonging to "clandestine structures" and of distributing illegal literature, and were excused from elaborating on the charges because of "state security."

Both the speed of the physicist's imprisonment and the scale of his offense indicated how the government of Gen. Wojciech Jaruzelski is rapidly refilling Poland's jails only six months after a "humanitarian initiative" to release political prisoners. Opposition activists and western diplomats here say that more than 250 persons are now being held for offenses ranging from attempting to organize protests to simply possessing illegally printed leaflets.

Since January, the number of detainees has grown at the rate of more than one per day, opposition sources said. Government officials have refused to release figures on political prisoners to western reporters since late last year.

Political prisoners once again have become a political and diplomatic sore point for Jaruzelski, who since last year has struggled to convince both western and eastern observers of Poland's "normalization." And again, government officials have begun hinting at preparations for an amnesty, potentially the fourth such release since 1983.

Increasingly, however, both government and opposition politicians are describing the jailing of political suspects -- and the occasional mass releases -- as an inevitable feature of Jaruzelski's standoff with an opposition he can neither accept nor totally eliminate. "It's become normal in this country," said one former prisoner. "The arrests are as predictable as the amnesties."

Ever since Jaruzelski suppressed the independent Solidarity Union in 1981, western governments and Poland's Roman Catholic church repeatedly have pressed for the freedom of jailed Solidarity activists. Yet while Poland's desperate need for western credit and Jaruzelski's hopes of compromise with the church have led him to arrange the periodic releases, communist principles and Soviet oversight have prompted him to continue repressing the extensive underground publishing and factory organization network to which most pardoned prisoners quickly return.

The result is that released grass-roots activists tend to be rapidly replaced in cells by their coworkers, while many leaders of the opposition movement have consistently returned to jail. "The game is that part of the people given amnesty give up their activism, and the group gets a bit smaller each time. But then new people join in," said Henryk Wujec, a veteran government opponent sentenced last week to a new three-month jail term. "It's become a war of attrition."

Both sides gradually have refined their tactics and weapons in this cyclical struggle. In particular, government authorities greatly increased their powers last year by sanctioning a law calling for summary proceedings in many political cases.

The measure has allowed the sentencing of scores of opposition activists and suspects to jail terms of up to three years on 24 hours' notice and with a minimum of evidence. "The rule of law has changed to a direct rule of police," charged Zbigniew Romaszewski, an opposition expert on political prisoners. "Summary proceedings have made trials a mere formality between arrest and imprisonment."

The government's growing dependence on summary proceedings was illustrated last week when courts around Warsaw dispatched the cases of dozens of persons arrested during May 1 opposition gatherings in a matter of hours. Though most persons were let off with heavy fines, one man was given a year in jail for attempting to intervene in a scuffle between several police and a woman who had taken their photograph.

At the same time, lawyers and opposition activists say security forces increasingly have adopted the tactic of placing political suspects in custody during criminal investigations that often last for months or even years without producing formal charges. While held in such "investigative arrest," political prisoners are isolated and generally suffer worse conditions than those who have been convicted and sentenced formally.

One of Poland's best-known political prisoners, writer Czeslaw Bielecki, was arrested in March 1985 but has still not been formally indicted for a crime. "From the point of view of the authorities, investigative arrest is the best repression of all," said Tadeusz Wypych, 34, who was released last December after serving seven months in investigative custody and only five months in normal prison wards. "No court action is required, and people can be imprisoned by the police even if there is no proof at all."

Opposition organizations have become skillful at chronicling and publicizing the cases of political prisoners both at home and abroad, damaging the government's image and making sustained repression politically impossible.

In recent months, a determined hunger strike by Bielecki and the publication in the United States of smuggled political essays by opposition leader Adam Michnik have helped to maintain the issue of prisoners as a barricade between Jaruzelski and improved relations with western governments, despite declining support for Solidarity in countries such as West Germany and France.