Ten years after the start of the AIDS epidemic in the Netherlands the proportion of persons infected by heterosexual contacts among the total of AIDS cases diagnosed is small (7.4%). Up to December 1991 the cumulative totals of females and males in the Netherlands reported with the diagnosis and infected by heterosexual contact were 55 and 93, respectively. Of the 55 heterosexual females, 69% had the Dutch nationality, of the 93 heterosexual males, 67%. Considerable proportions of the numbers of AIDS patients in this group (males 47%, females 45%) were diagnosed in the four largest cities (Amsterdam, Rotterdam, The Hague and Utrecht). The remaining cases of AIDS diagnosed in this group were scattered throughout the country. Among heterosexual females a gradual increase of the number of AIDS cases diagnosed was observed since 1985. In the males there was no clear trend in the number of diagnoses since 1984. Of the 55 females, 19 originated from an area endemic for AIDS or had had sexual contacts with a person from such a region (34.6%). Among the 93 males this number was 29 (31.2%). Nineteen of the 55 females (34.6%) were known to have sexual contact with a person from the known risk groups. The same held true of 12 males (12.9%). Of the remaining 17 females (30.9%) and 52 males (55.9%) it was only known that they were heterosexual without further risk factors or risk contacts.(ABSTRACT TRUNCATED AT 250 WORDS)