Six cases, totaling seven supernumerary mandibular premolars, were seen in a sample population of 4,000 patient records. Four were from a suburban private practice sample of 2,000, the others from a similar group randomly drawn from an urban dental school. Five of seven appeared on the left side, six of seven were impacted or erupted ectopically. Only one patient was female. Four were of Spanish or Hispanic descent, one was white and one was black. The only other supernumerary teeth seen in the population sampled were two paramolars and one mesiodens. The recommended course of treatment is extraction of the supernumerary teeth, unless they may be useful for orthodontic purposes or if the surgery would be unjustifiably hazardous to adjacent structures. Complications could result in resorption of other teeth, malocclusion, and possible cystic degeneration and ameloblastoma formation.