OBJECTIVE Identify types, prevalence and severity of periodontal changes associated with HIV infection. DESIGN: Cross‐sectional controlled blinded study. SETTING: Open access genito‐urinary medicine clinic. PARTICIPANTS: Convenience sample of 794 homosexual men aged 18–65.OUTCOME MEASURES: Prevalence, extent and severity of probing attachment loss (PAL), pocketing, gingival ulceration, gingivitis, bleeding on probing (BOP), gingival red bands and diffuse and punctate erythema of the attached gingiva (selecteda priori).RESULTS: Prevalences in men with (n = 312) and without HIV (n = 260) were: PAL (≥l site ≥4 mm), 59.6% and 28.5% respectively (P<0.001. x2); pocketing (≥1 site ≥4 mm) 51.0% and 31.9% (P<0.001); BOP, 96.5% and 92.3% (P = 0.038); gingival ulceration. 3.2% and 1.0% (P = 0.031), red banding, 12.2% and 10.0% (P = 0.410); diffuse erythema, 12.5% and 3.1% (P<0.001) and punctate erythema, 9.6% and 1.1% (P<0.001). Decreased CD4 lymphocyte counts predicted the presence, extent and severity of PAL (P = 0.023, 0.027 and 0.060) but not pocketing. Oral candidiasis predicted the extent and severity of gingivitis and the presence of diffuse and punctate erythema (P = 0.037, 0.011, 0.002 and<0.001).CONCLUSIONS: Destruction of periodontal attachment is associated with progression of HIV disease whereas pocketing is associated with HIV infection but not disease progression. Gingival ulceration is associated with HIV but gingivitis and erythema of the attached gingiva are most strongly associated with oral candidiasis. Gingival red bands were not associated with