High-grade squamous intraepithelial lesions of the cervix are heterogeneous in their invasive potential. Comparison of human papillomavirus types between invasive cervical carcinoma and high-grade squamous dysplasia may provide insight into this biological variability. Liquid-based Pap specimens from 55 high-grade intraepithelial lesions and 47 invasive cervical carcinomas were analyzed by reverse line blot for 27 human papillomavirus types designated high, intermediate, or low risk. Human papillomavirus DNA was present in all high-grade intraepithelial lesions (23 different types) and in 94% (13 types) of invasive carcinomas. High-risk types were present in 81% of invasive carcinomas compared to 58% of high-grade intraepithelial lesions. Severe dysplasias harbored more (79%) high-risk human papillomaviruses as compared to moderate dysplasias (37%). In 40% of high-grade dysplasia cases (59% of moderate dysplasias; 21% of severe) and 13% of invasive carcinomas, intermediate-risk genotypes were identified in the absence of high-risk HPV types. Human papillomavirus 16 was the most common type in all categories, including 47% of high-grade squamous dysplasias (26% moderate; 68% severe) and 61% of invasive carcinomas. Both high-risk type (P=0.0004) and type 16 (P=0.0007) human papillomaviruses were positively associated with increasing severity of diagnosis. The heterogeneous nature of high-grade squamous dysplasias as compared to invasive carcinoma is evident by the wider spectrum of associated human papillomavirus types. Likewise, moderate dysplasia appears to be more heterogeneous in viral type than severe dysplasia. Moderate cases were more often associated with intermediate-risk types, while high-risk types were more prevalent in severe dysplasias and invasive cancers. Moderate dysplasia cases harboring viral types infrequently found in cancers may have a low risk for progression. Human papillomavirus genotyping of high-grade squamous intraepithelial lesions may be important in assessing risk for progression to invasion.