A prospective study of hands with Dupuytren's contracture was designed to test the association of three variables, the presence of an interdigital soft tissue mass, the presence of flexion contractures at each digital joint, and the duration of contracture, with the formation of spiral nerves. 66 digits in 37 hands affected by Dupuytren's disease were examined intra-operatively. Of the 34 digits (52%) with spiral nerves, 28 had soft tissue masses (42%). The sensitivity of a soft tissue mass alone as a predictor of a spiral nerve was 59% and the specificity 75%. The presence of a flexion contracture at the PIP joint had a sensitivity of 88% and a specificity of 62% for the presence of a spiral nerve. The combination of a soft tissue mass and a PIP joint contracture was a very specific (94%) but not a particularly sensitive (50%) test for spiral nerve formation. The formation of a spiral nerve is progressive, occurring most often in hands with significant PIP joint contractures with or without soft tissue interdigital masses.