Three techniques (transmitted light, polarizing light and scanning electron microscopy) were used to describe and study the pattern of growth layer groups (GLGs) in the teeth of Chilean dolphin, Cephalorhynchus eutropia. Samples included teeth from 36 dolphins. No significant sexual differences were found in the decalcification time. The GLG pattern was similar to the pattern described for other delphinids. The number of estimated GLGs in the sample ranged from 1.0 to 19.0. Polarizing light revealed incremental layers in the predentine, three pairs of bands in the neonatal line, and 12-13 incremental layers within each GLG. Cemental GLGs were difficult to observe by the three techniques, because their limits were diffusse.