Brain tumor-polyposis (BTP) syndrome is a rare genetic disease characterized clinically by the concurrence of multiple colorectal adenomas and primary brain tumors. The BTP syndromes can be subdivided into two major categories based upon clinical phenotype, modes of inheritance and underlying gene mutations. Type I BTP syndrome (Turcot’s syndrome) is characterized by the presence of malignant gliomas and multiple benign colorectal adenomas in the second or third decade. The frequent presence of consanguinity and the absence of parental disease indicate that Type I BTP syndrome is inherited in an autosomal recessive manner. The genes responsible for Type I BTP syndrome include the mismatch repair (MMR) genes, which are also linked to hereditary nonpolyposis colorectal cancer (HNPCC, or Lynch syndrome). The original BTP case described by Turcot fits into this category.