A sample of 60 kindergarten and grade 1 children was administered conservation of number tasks. The effects of three variables on conservation of number were measured (familiarity the degree of familiarity of the materials; orderthe order of presentation of the materials; attachmentthe nature of the relationship between the two rows of materials used in conservation of number tasks). Of these three variables, only familiarity was significant. Children appear to find conservation of number easier when tested with materials familiar to them as compared to unfamiliar materials.