The current study examined the capacity of the Theory of Planned Behaviour (TPB) and the Prototype/Willingness model (P/W model) to predict intention to have unsafe sex with new and regular partners as well as frequency of unsafe sex in a sample of men who have sex with men (MSM) sample. The study also examined aspects of the sexual situation immediately prior to or during unsafe sexual intercourse (such as substance use, venue and emotional state) to determine whether there were any significant correlations and group differences. One hundred and fifty-eight male participants between the ages of 18-26 who have had sex with another male in the last nine months completed an online survey of sexual habits, TPB and P/W model variables. With the exception of prototypes, the results showed significant group difference in terms of TPB and P/W model variables between risk groups. Furthermore, there was no significant difference between models in predictive capacity in terms of either intention or frequency of unsafe sex. The results of the study suggested participants were generally only having unsafe sex with regular partners, that in older samples it may be more parsimonious to use the TPB than P/W model and that it is important to measure TPB variables in terms of both new and regular partners for increased accuracy and greater applicability in terms of HIV/STI interventions.