In contrast to previous research which has largely focused on students
' perceptions of other students' risk for contracting HIV/STDs, this s
tudy assessed single heterosexual college students' (96 men, 121 women
) perceptions of the prevalence of different sexual behaviours which i
ncrease a person's risk for HIV/STD infection (e.g. multiple sexual pa
rtners, unprotected sexual intercourse, one-time sexual encounters). C
onsistent with previous research which has demonstrated an overestimat
ion bias in judging others' risk for HIV/STD infection, students' esti
mates about the prevalence of sexual behaviours increasing a person's
risk for HIV/STD infection were similarly overestimated relative to re
ported base rates. Gender differences were also observed. Although wom
en generally tended to give higher prevalence estimates than men, over
all, participants gave higher estimates when judging the behaviour of
men compared to women. Both motivational and cognitive explanations of
our data are discussed. Our findings highlight the importance of deve
loping sexual risk reduction programmes which (a) enable students to m
ake more accurate personal risk judgements, (b) increase students' awa
reness of the riskiness of their own sexual behaviours, and (c) promot
e positive health changes (e.g. increased condom use) in normative sex
ual behaviour among college students.