Although a number of observers have reported cases of congenital absence of patellae, yet out of six standard textbooks of anatomy consulted, only one (Piersol's) calls attention to this anomaly. It says: Congenital absence of the patella on one or both sides has been noted in a number of instances, and has in some cases been observed in several members of the same family. The functional disability was slight or altogether unnoticeable. These observations agree perfectly with the findings in cases here presented. Another anomaly which exists in two of the three cases is an incomplete development of the thumb nails. The two conditions, namely, absence of patellae and absence of thumb nails, are strangely correlated. Little1collected eighteen cases in a family of four generations in which there were no patellae and no thumb nails. He does not state whether the two conditions coexisted in all the cases