This report describes the age, growth, and reproductive biology of the spiny dogfish Squalus acanthias off the northeastern U.S. Analysis of growth rings on dorsal fin spines yielded yon Bertalanffy growth coefficients (K) and asymptotic total lengths (L∞) of K = 0.1481, L∞= 82.49 cm for males, and K = 0.1057, L∞= 100.5 cm for females. Median lengths and ages at maturity were 79.9 cm and 12.1 years for females and 59.5 cm and 6.0 years for males. The average number of young for females at the modal size range (90–94 cm) was 5.8; litter size ranged from 1 to 15 embryos every 2 years.