MEN syndromes (1 and 2) are hereditary tumor syndromes inherited as autosomal dominant traits. The genes that harbor the mutations responsible for the development of these syndromes have been cloned in recent years. In the present study we applied an "in silico" approach to find previously undescribed sequence variants of the RET protooncogene and the MEN1 gene. Sequence comparisons were performed at the National Center for Biotechnology Information Database by the search tool blastn. We found several sequence alterations in both coding and non-coding sequences. The majority of polymorphisms described to date were found by our approach, in addition we observed novel sequence variants of both genes as well. These sequence variants may have both diagnostic and theoretical relevance. In silico strategies may represent new, and potentially effective ways for finding novel sequence variants.