Cytogenetic analyses of benign tumors in the past 2 decades have established consistent and recurrent abnormalities in a large proportion of these tumors. In particular, chromosomal analyses of meningiomas, adenomas of the salivary gland, uterine leiomyomas and lipomas have led to the identification of cytogenetic subtypes characterized by specific structural or numerical abnormalities. A comparison of these consistent changes shows a clustering of aberrations to specific regions on chromosomes 12, 1, 2, 6, 11, 13 and 22. The specificity of the involvement of these chromosome regions in the various benign neoplasms suggests that genes of importance in growth regulation rather than those related to malignant transformation are located at these sites.