Officials and inmates were wary when the state prison here began housing women, as well as men, earlier this year. But of all the potential problems that crossed their minds, there is one that no one anticipated: how difficult it would be for the prison store to keep men's cologne in stock.

''We're acting more gentlemanly,'' said Charles Johnson, a 27-year-old inmate serving time for murder at Logan Correctional Center. ''We want to look nice and smell nice, too.'' #72 Women Among Inmates Logan, which began taking women in March to relieve overcrowding at the Illinois penitentiary for women, now has 72 women among 842 prisoners. While women have been imprisoned with men at work camps and minimum-security facilities, Logan is the nation's only coed medium-security prison.

In the last five years, the number of women in the nation's prisons has increased at a rate double that of men. And the number of coed prisons has more than doubled, to 89, in the last 10 years, said Charlotte Nesbitt, a spokeswoman for the American Corrections Association. Still, she said, women account for less than 5 percent of the nation's prison population.

''At first, I didn't like the idea of being in prison around men,'' said Marcia Kelly, who is serving time for a forgery conviction, as she sat in a library lounge next to Mr. Johnson. ''But it's more normal this way.''