The northern-offshore-spotted-dolphin (Stenella attenuata) age-determination project began in the fall of 1980 with the purpose of obtaining ages for a large sample of specimens. Although a smaller sample from this stock of dolphins had been aged in a previous study (Perrin, Coe, and Zweifel, 1976), the number of available specimens has increased nearly five-fold and includes data spanning 12 years. In addition, cetacean age-determination techniques have been refined. Age estimates are assumed to be more accurate with current techniques because the resolution of growth layers groups (GLGs, terminology of Perrin and Myrick, ed., 1980) is better, and the interpretation of GLGs is thought to be more accurate. The large number of age readings made in this sample required that a data base be created and that a system for editing the data be established.

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