Rates of HIV testing are increasing among men who have sex with men (MSM) in Scotland and the UK. However, it remains vital to encourage MSM to test for HIV. The aim of the current study was to determine which factors discriminated among three groups of MSM: those tested for HIV within the previous year, those who had tested over one year previously, and those who had never tested. Cross-sectional data were collected using self-report, anonymous questionnaires from MSM frequenting gay venues in Glasgow, Scotland, during July 2010 (N = 822, response rate 62.6%). Those who identified themselves as HIV positive (n = 38), did not normally reside in Scotland (n = 88), and did not provide information on HIV testing (n = 13), were excluded (139 excluded, leaving N = 683). Around 57% (n = 391) had tested for HIV within the previous year, 23% (n = 155) had tested over one year previously and 20% (n = 137) had never tested. Compared with those tested within the previous year, those tested over one year previously and those never tested had greater fear of a positive-HIV test result, a weaker norm for HIV testing, and were more likely to have had no anal sex partners at all within the previous year. Those tested over one year previously were significantly older than both other groups (who were more likely to be under 25 years of age). Unprotected anal intercourse (UAI) did not discriminate among the HIV testing groups. The results highlight the need to promote HIV testing in Scotland among those under 25 years and over 45 years, those with high fear of testing, and those whose sexual behaviour puts them at risk. Interventions to increase HIV testing should promote positive norms and challenge the fear of a positive result.