Abstract Background Morphologic criteria which might help to support the need for a preventive strategy for early detection of rectal cancer were analysed. Population-based data on rectal adenomas with high-grade dysplastic changes (n = 199) and invasive adenocarcinomas (n = 912) registered by the national Morphologic Tumour Registry (MTR) and diagnosed in a central department of pathology in Luxembourg between 1988 and 1998 were considered. Methods The analysis concerned time trends in frequency, crude incidence, tumour-stage, the rectal "high-grade" adenoma/invasive adenocarcinoma-ratio and the survival rates. Histopathological tumour-stage parameters (UICC/AJCC, 1997) in a consecutive series of 641 resected rectal cancers and their relationship with the observed patient survival are investigated. Results The majority of invasive adenocarcinomas are diagnosed at a late stage (i.e. Stage II and III) into contrast with the highly significant increase (355 %) in frequency of rectal high-grade adenomas (Stage 0). During the two-time periods 1988–1992 and 1994–1998 Stage I and Stage IV-cases decreased by 11 % and 47 % respectively. Tumour-stage correlates with prognosis. The rectal high-grade adenoma / invasive adenocarcinoma-ratio improved significantly over the last five years. Conclusion Over the study period, there has been a highly significant rise in the incidence of resected rectal adenomas with high-grade intraepithelial neoplasia. The ratio of early tumours to invasive cancers has risen while the numbers of colonoscopies and rectoscopies remained unchanged respectively decreased. As the number of advanced tumour-stages remained stable, mass-screening procedures focusing on the fifty to sixty age group should be reinforced.