The Swedish Family-Cancer Database was used to analyse familial relationships in mothers and daughters with invasive and in situ cervical cancers by histological type during the years 1958-1996, including a total of 21,727 and 191,081 cases, respectively. Familial standardized incidence ratios (SIRs) were calculated separately for mothers and daughters and for invasive and in situ squamous cell carcinoma (SCC) and adenocarcinoma. Familial risks were about 2.0 in invasive SCC and less in in situ SCC. Limited analyses could be carried out on adenocarcinoma because the number of cases was small. However, familial risks were not much smaller in families where only SCC was diagnosed compared with those where both SCC and adenocarcinoma were present. A comparison of cancers between mothers and daughters showed an association between cervical cancer and SCC of skin, and between cervical cancer and smoking-related cancers. The familial risks were unaffected in Poisson regression analysis on many possible intervening variables. The data suggest that host factors modulate an individual's response to human papillomavirus infections.