OBJECTIVE: To describe the outcome of patient referral at the STD clinic of the University Hospital Rotterdam. To study characteristics of heterosexual index patients and partnerships related to referral outcome. METHODS: In 1994, patients with gonorrhoea and chlamydia were referred to public health nurses for interview and patient referral. Referral outcome was classified as "verified" if partners attended the STD clinic and as "believed" if partners were said to have attended elsewhere. RESULTS: Of 454 patients, 250 (55%) participated in the study. The outcome of patient referral for the 502 eligible partners was 103 (20.5%) verified referrals, 102 (20%) believed referrals, and 297 (59%) with unknown follow up. Of the 103 partners examined, 43 had an STD of which 63% reported no symptoms. The contact finding ratio was higher for chlamydia patients and heterosexual men. Also, referral was more effective for index patients with recent sexual contact, with follow up visits to the public health nurse, for men who were not commercial sex worker (CSW) clients, and, to a lesser degree, for Dutch patients and patients who sometimes used condoms. For steady partners, referral was improved if the last sexual contact was more recent. Casual partners visited the clinic more often if sexual contact occurred more than once, if the last contact was more recent, if they were older, and if they were Dutch. CONCLUSIONS: Patient referral was more effective for certain groups, such as chlamydia patients and steady partners, but was inadequate for others, including CSW and their clients, other "one night stands", young partners, and ethnic minorities.