Total yearly growth of smallmouth bass,Micropterus dolomieuiLacépède, of ages 3–5 in South Bay, Lake Huron, and in several other widely scattered populations was related to mean surface water temperature for the period July through September, more growth being associated with warmer waters. No such relationship was demonstrated for bass of the same ages in Lake Opeongo, Ontario, nor for older bass in Lake Opeongo and South Bay. The difference in the manifestation of a growth–temperature relationship appears to be real, rather than a result of differences in data or treatments of them, and indicates, therefore, that other factors may influence total annual growth as much as, or more than, temperature.