The effects of population density on shape and size of cylindrical red beet genotypes were evaluated in a field experiment during 1994 and 1995. Two F1 hybrids and two open-pollinated genotypes were planted in replicated trials consisting of three population densities. Yield, harvest weight, percent harvestable beets per plot, length, middle width, top width, bottom width, length × width, length to width ratio, and a shape index (SI) were measured on a sample of beet plants from each plot. The density × genotype interaction was nonsignificant for all 10 traits. Averaged over genotypes, significant differences among densities were found for harvest weight, percent harvestable beets per plot, length, middle width, and length × width. In general, greater harvest weights, a higher percentage of harvestable beets, and greater length, middle width, and length × width values were found at low density. Averaged over densities, significant differences among genotypes were measured for all 10 traits. The open-pollinated genotypes Cyndor and Cylindra exhibited lower yield, lower harvest weight, greater SI, and a higher percentage of harvestable beets than their hybrid counterparts. These data demonstrate that population density has a differential and significant effect on the shape and size of cylindrical beet genotypes.