The primary aim of this study was to describe patients at sexually transmitted disease (STD) clinics in Cape Town, South Africa, in terms of gender, education and age differences relative to their STD knowledge and beliefs, their condom use, as well as their attitudes towards condom use and their condom-use behaviour. The information was collected with a view to developing a health education intervention. Structured interviews were conducted with 2978 randomly sampled Xhosa-speaking STD clinic attenders about their knowledge, beliefs and practices regarding STDs and related behaviours. More males (75%) than females (25%) presented for STD treatment. The majority of patients (92%) were younger than 35 years. Female patients were found to be more aware than male patients of the sexual nature of STD transmission, valued personal autonomy in sexual behaviour and expressed a greater need to use condoms. Males perceived STD symptoms to be more serious, had more misconceptions about the cause of STDs and also more negative beliefs and attitudes towards condom use. Only 34.9% of the patients reported using condoms in the last 6 months while only 24.5% reported regular use. Those who reported condom use were more knowledgeable about the sexual transmission of STDs and the effects of STDs on the neonate. They also had fewer misconceptions about the causes of STDs and perceived STD symptoms to be more serious, attached greater value to personal autonomy in sexual behaviour and condom use and had more positive outcome expectancies of refusing sex than those who never used condoms. The data suggest that targeted interventions directed at males will have to address their inadequate knowledge regarding STDs in terms of transmission, causes, consequences, prevention and cure. Their negative beliefs and attitudes towards condoms will need special attention, especially in view of their multiple partner behaviour. Interventions directed at females will need to improve their knowledge regarding STD consequences, causes, recognition of symptoms as well as improve their knowledge of aspects of prevention and cure. All interventions must facilitate personal autonomy in decision making about sexual behaviour and condom use for both men and women, through skills development programmes that promote self-efficacy in the individual and instil a culture of mutual respect of such in the community.