The frequency of high-risk human papillomavirus (hr-HPV) genotypes in patients with adenocarcinoma in situ (ACIS) with coexisting cervical intraepithelial neoplasia (CIN), ACIS without coexisting CIN, and high-grade CIN (CIN II/III) was studied, in order to gain more insight into the relation between hr-HPV infections and the development of coexisting squamous and glandular lesions. The SPF 10 LiPA PCR was used to detect simultaneously 25 different HPV genotypes in biopsies obtained from 90 patients with CIN II/III, 47 patients with ACIS without coexisting CIN, and 49 patients with ACIS and coexisting CIN. hr-HPV was detected in 84 patients (93%) with CIN II/III, 38 patients (81%) with ACIS without CIN, and in 47 patients (96%) with ACIS and coexisting CIN. A total of 13 different hr-HPV genotypes were detected in patients with CIN II/III, and only five in patients with ACIS with/without coexisting CIN. HPV 31, multiple hr-HPV genotypes, and HPV genotypes other than 16, 18, and 45 were significantly more often detected in patients with CIN II/III, while HPV 18 was significantly more often detected in patients with ACIS with/without CIN. There were no significant differences in the frequency of specific hr-HPV genotypes between patients with ACIS with or without coexisting CIN. In conclusion, the frequency of specific hr-HPV genotypes is similar for patients with ACIS without CIN and patients with ACIS and coexisting CIN, but is significantly different for patients with CIN II/III without ACIS. These findings suggest that squamous lesions, coexisting with highgrade glandular lesions, are aetiologically different from squamous lesions without coexisting glandular lesions. . Numerous studies have suggested that the development of squamous cervical carcinoma is preceded by cervical intraepithelial neoplasia (CIN) (Wright et al, 2002;Bosch et al, 2002).The frequency of hr-HPV genotypes in CIN lesions has been studied previously and its detection rate rises with increasing severity of the CIN lesion (Bekkers et al, 2002a;Bosch et al, 2002;Wright et al, 2002). Only limited studies are available on the frequency of hr-HPV genotypes in premalignant glandular lesions and the number of patients in most studies is rather low (see Table 1) (Colgan and Lickrish, 1990;Leary et al, 1991;Higgins et al, 1992;Duggan et al, 1995;Anciaux et al, 1997;McLachlin et al, 1997;Pirog et al, 2000;Riethdorf et al, 2000Riethdorf et al, , 2002Madeleine et al, 2001). High-risk human papillomavirus was detected in 66 -100% of patients with ACIS (Anciaux et al, 1997;Riethdorf et al, 2000). Approximately 48% of all women diagnosed with ACIS have coexisting squamous lesions (Colgan and Lickrish, 1990;Leary et al, 1991;Higgins et al, 1992;Duggan et al, 1995;Anciaux et al, 1997;McLachlin et al, 1997;Pirog et al, 2000;Riethdorf et al, 2000Riethdorf et al, , 2002Madeleine et al, 2001), but the frequency of specific hr-HPV genotypes in patients with ACIS has not been studied in relation with the presence or absence of coexisting CIN lesions. In this stu...