SynopsisThe effectiveness of phenotypic recurrent selection was measured in four successive cycles on first year growth of biennial yellow sweetclover. Results from this study show that changes per cycle, as measured in terms of variances and population means, were greater for a plant character with high heritability than for a character with a lower heritability. The progress made suggests that phenotypic recurrent selection may be an effective means for modifying an unselected population to improve uniformity in growth type and plant vigor.