The purpose of this study was to assess the accuracy of injections of dye into the first extensor compartment of the wrist using three different techniques in 150 wrists in 75 fresh cadavers. To compare injections, 50 wrists from 25 cadavers were used for each technique. After the injections, the first extensor compartment was dissected and the dispersion of dye around the abductor pollicis longus and extensor pollicis brevis tendons was investigated. In 72 % of all the wrists, acrylic dye was dispersed into one compartment containing both the abductor pollicis longus and extensor pollicis brevis tendons, but in 28% of the wrists there was a separate compartment for extensor pollicis brevis and dye entered only one of the compartments (14% for each compartment). For accurate injections, we think the injections should be made separately over the two tendons, to allow for the possibility of a septum within the compartment.