Yellow bass age and growth data were obtained from 202 fish collected in Lake Poygan, Wisconsin, a 5,707-hectare widening of the Wolf River, during October, 1963 and winter of 1963-64. The fish length-scale length relationship was L = 15 + 1.529 (R). No significant difference in growth between sexes was found. The growth of Lake Poygan yellow bass was greater than that reported from most areas. All fish were mature at age-group III. The length-weight relationship was log W = −4.0289 + 2.7000 log L, where W = weight in g and L = total length in mm.