The most common deformities of the metacarpus occur in conjunction with poly- and oligodactyly. The authors first refer to the most important operations in treating these deformities and emphasize that in certain cases solitary resection of surplus fingers is not enough: in addition, outgrown articular process must be removed, bent metacarpals osteotomised and capsular defects closed. The treatment of oligodactylic hands is made difficult by cutaneous and osseous syndactyly. The operating surgeon should have sufficient experience in plastic surgery to be able to take care of severe adduction contractures of the thumb with constriction of thumb commissure. For aplasia and hypoplasia in the thumb ray the already proven index finger pollizisation is thetherapy of choice. Triphalangeal thumbs are operated according to the same principles. On the other hand in brachyphalangeal thumbs commissure increase and correction of the clinodactylia are of prime importance. Phalangisation is very rewarding in certain forms of synbrachydactyly. In some deformities only the thumb is present. In these cases we recommend an opposition post built out of a tubed flap and autogenous bone graft. Some examples of defective hands surgically treated are shown.