Otoliths (lapilli) were used to age two catostomid fishes, black redhorse (Moxostoma duquesnei) and golden redhorse (Moxostoma erythrurum), from three White River and one Arkansas River tributary in southwest Missouri. Populations in the James River (White River system) were sampled monthly for one year, and edge analysis was used to determine timing of otolith annulus formation. Both species formed a single opaque annulus in otoliths during May and June. Maximum ages estimated from otolith annulus counts were 11 years for black redhorse and 12 years for golden redhorse. Age classes 2 and 3 dominated populations for both species. Fish length at age was modeled with von Bertalanffy growth models; parameters were k  =  0.39 and L_∞  =  385 for black redhorse and k  =  0.31 and L_∞  =  377 for golden redhorse in James River populations.