Using a monofilament wire suture, the radial and ulnar edges of the flexor retinaculum were approximated in 14 white New Zealand rabbits. As a result, the volume of the carpal tunnel was diminished, and "carpal tunnel syndrome" was produced. At various intervals after this procedure the animals were sacrificed. The median nerve and all the digital flexor tendons passing through the carpal tunnel were excised "en bloc", and sent for histological examination. Vascular proliferation with perivascular round cell infiltration and oedema, and large areas of fibroblastic activity were observed around the digital flexor tendons. This was probably due to increased vascular permeability secondary to ischaemic endothelial damage. These findings are similar to those observed in the synovium of patients operated on for carpal tunnel syndrome.