Although serological reactivity to human papillomavirus type 16 (HPV-16) proteins has been demonstrated in patients with invasive cervical carcinoma, the degree of seroreactivity to these proteins in women with preinvasive disease and its relationship to the HPV type associated with the disease are unclear. We obtained sera from 27 women undergoing cone biopsy for cervical precursor lesions and 22 controls and analyzed seroreactivity by Western blot to fusion proteins containing portions of the HPV-16 E4, L1 and L2 open-reading frames (ORFs). Positives were analyzed by scanning densitometry and intensity values for each case plotted relative to controls. Cervical biopsy specimens from patients were analyzed for HPV-16 nucleic acids by DNA.DNA in situ hybridization. Mean intensity values for seroreactivity to the pATH-E4 protein approached significance (P = 0.058) and a significantly higher proportion of cases vs controls registered values over 4.0 for pATH-E4 (26% vs 4.5%; P = 0.04) and pATH-L2 (48% vs 18%; P = 0.03) proteins. A significantly higher mean intensity value for E4 was observed for cases containing HPV-16 DNA vs HPV-16 negative cases or controls. Thus, seroreactivity to HPV-16-derived proteins may be more common in women with preinvasive cervical disease, and for some protein targets (E4) may indicate a relatively type-specific response.