Tadpoles of Bufo bufo at the end of premetamorphosis were exposed to the action of retinol diluted in the rearing water at two concentrations: 20 and 40 microM, for 48 h. Assuming that retinol causes growth suppression by cell death induction, the TUNEL reaction for the detection of apoptotic cells was performed on paraffin sections of pancreas. The results showed that retinol induced a significant dose-dependent increase of number of apoptotic cells with respect to controls, in which apoptosis was scarce. Electron microscopic observations of treated specimens showed that the effects of retinol mostly occurred on exocrine cells: condensed crescent-shaped nuclear chromatin, dark cytoplasm with long projections; conversely, mitochondria and endoplasmic reticulum appeared unaffected.