OBJECTIVE--To ascertain factors associated with genital pediculosis and scabies infestations among attenders at an STD clinic. DESIGN--Cross sectional assessment of potential risk factors by multiple logistic regression. SETTING--A central city sexually transmitted diseases (STD) clinic in Adelaide, South Australia. SUBJECTS--All men and women patients attending from 1988 to 1991. RESULTS--Pediculosis pubis was diagnosed in 205 of 12,170 (1.7%) men and 65 (1.1%) of 6125 women, and scabies in 56 (0.5%) men and 6 (0.1%) women attending an STD clinic from 1988-1991. Independent risk factors by multivariate analysis for pediculosis pubis in women were pregnancy (odds ratio (OR) = 2.3), sex outside the state (OR = 2.2) and age under 25 (OR = 2.0). Many factors were associated with pediculosis pubis in men, including no steady partner (OR = 1.4), multiple partners (OR = 1.6), being unmarried (OR = 2.0) and homosexual behaviour (OR = 1.6). None of these factors was associated with scabies infestation which was strongly associated with being Aboriginal (OR = 6.8) and being unemployed (OR = 2.5). CONCLUSION--In this setting scabies appears to be determined by socioeconomic factors and pediculosis pubis predominantly by sexual activity factors.