Between 1 March 1985 and 28 February 1987, 1659 patients attending Glasgow Genito-Urinary Medicine (GUM) Clinics were tested for antibodies to human immunodeficiency virus (HIV). Forty (2.4%) were positive. Thirty-seven of these were homosexual (36/37) or bisexual (1/37) males. The overall prevalence of antibodies to HIV in this group was 3.9% (37/940) and showed no significant increase over the two year period. Following the extensive media campaign in October 1986, the total numbers tested each month rose from an average of around 50, to 144 in December 1986. There was a further rise to 220 in March 1987 coinciding with AIDS week in March 1987. Since then the numbers have again declined. Before the October campaign, 70% of these tested (692/990) were homo/bisexual males. After the campaign the number of heterosexual males and females rose sharply, accounting for 68% of these tested.