The hair-dye component resorcinol was tested for potential in vivo induction of sister-chromatid exchanges (SCE) in bone-marrow cells after intraperitoneal, peroral and epicutaneous application to rats. None of the tested drug concentrations produced an increase in SCE frequencies. As a control for our test method we demonstrated dose-dependent SCE increases induced by 2-acetylaminofluorene and by 2-aminoanthracene, cytogenetic response to 2-aminoanthracene being higher in females than in males.