The quality of proxy reporting was assessed among 136 prenatal patients and their spouse/partners recruited from the obstetric services of a New Jersey hospital between 1985 and 1987. The concordance, sensitivity, and specificity of proxy reports about partners' occupation, smoking, and drinking were examined in relation to self-reports. Overall, private patients provided better proxy data than did clinic patients, and women provided better data than did men. No consistent effects on the quality of proxy reports were found in relation to age, level of education, marital status, or length of cohabitation. Partners' recent job titles appeared to be quite accurately reported, whereas partners' smoking and drinking patterns were less well-reported. For alcohol use in particular, there was evidence of considerable misclassification resulting from proxy reports even when kappa statistics and intraclass correlation coefficients suggested good agreement. Use of proxy respondents is unnecessary in reproductive studies and should be avoided when it may produce misleading results. Our data indicate that private prenatal patients and their partners can give reasonable proxy reports about job titles and smoking, but not about alcohol use. The high proportion of clinic patients who did not refer a partner (or whose partners could not be contacted) limits the generalizability of our results for this group and gives cause for concern about collecting proxy information from clinic populations.