Seventy-two cases of in situ adenocarcinoma (AIS) of the cervix were reviewed. Forty-five cases had associated cervical intraepithelial neoplasia and 20 cases had changes of wart virus infection. Five cases had associated microinvasive squamous cell carcinoma and one cases showed frankly invasive squamous cell carcinoma (SCC). Of the 72 cases, 41 showed an endocervical type of AIS and three cases an endometrioid type. There was no case of pure intestinal type AIS. Twenty-eight cases showed a mixed pattern. Architectural patterns characterized by tunnel clusters, cribriform glands, glandular budding and papillary formations were assessed. Most cases showed varying combinations of these patterns but in ten cases significant changes were absent. Both cellular apoptosis and mitotic activity were seen in varying degrees in all cases of AIS. The significance of these and other features of AIS are discussed as well as the conditions involved in the differential diagnosis.