Previous literature indicates the opercular bone as a useful tool for the determination of age and growth of fish. The reliability and validity of this method is tested for two populations of Utah chub. Age and growth are calculated for 222 Utah chub collected from Panguitch Lake and 212 Utah chub collected from Navajo Lake, southern Utah, in 1952-1953 from both scales and opercular bones. Scales are measured with the aid of a projector. Opercular bones are measured directly. The center of growth of the opercular bone is posterior to the posterior lip of the fulcrum. Correction for curvature is necessary in opercular bone measurements. The body-scale relationships for both populations are linear. The body-opercular bone relationships for both populations are slightly curvilinear. Agreement of dominant age classes for successive years, agreement of empirical length-frequency modes of young fish with calculated length-frequency modes of lower age classes, agreement of ages as indicated by scales and opercular bones, agreement of age with sexually immature fish and an increase in length with an increase in age are accepted as evidence for both methods. Opercular bones have less variation for calculated lengths in older age classes while the scales have less variation in the younger age classes. The scale method is a generally more efficient method for determining the age and growth of the Utah chub.