The incidence of undetected errors in one aspect of unit dose dispensing found in two methods of quality control is compared. In one method, a technician fills the unit dose box and a pharmacist checks each box. In the second method, a technician fills the box; a second technician checks the box. Pharmacist control and responsibility are maintained by having a pharmacist check a random sample of filled boxes. It was determined in this study that the incidence of undetected errors did not differ significantly between these two control methods.