Having observed an anomalous insertion of the lumbrical muscle in 74 consecutive operations for correction of camptodactyly of the small finger, we have concluded that the loss of normal lumbrical action is the principal cause of the intrinsic minus deformity seen in this condition. Other anatomic abnormalities observed in this series of patients are those of the superficial tendon in 47%, the x-ray appearance of the proximal interphalangeal (PIP) joint in 15%, and a fixed flexion contracture of the PIP joint in 66%. Fifty-seven percent of our patients had PIP flexion contracture of more than 45 degrees. To determine the contribution of these anomalies to this deformity, we analyzed a series of 53 patients who had been followed up for at least 1 year. The study revealed that these conditions are interdependent and that each had an adverse effect on the final operative results. Treatment included a transfer of the superficial tendon of the ring or little finger to the extensor mechanism of the little finger in all cases and other procedures as dictated by the individual situation. Overall, the joint contracture was reduced from 49 degrees to 25 degrees, but only 33% of the patients regained full flexion of the small finger.