A number of recent reports suggest that intracellular calcium concentration is increased in skeletal muscle in Duchenne muscular dystrophy (DMD). Leucocyte chemiluminescent responses are dependent on calcium ions and can be induced by the calcium ionophore A23187. Chemiluminescence may therefore reflect intracellular calcium levels. In order to determine whether non-muscle cells in DMD share the calcium abnormality, we have examined A23187-induced chemiluminescence in DMD leucocytes. Peak calcium dependent chemiluminescence occurred at 0.25-0.75 mM added calcium chloride. Peak chemiluminescent responses in the 13-paired samples were reduced in DMD leucocytes (P < 0.01) using a paired t-test. These results suggest that there is an abnormality of calcium dependent A23187-induced chemiluminescence in DMD leucocytes and that there may be a generalised abnormality of calcium metabolism in DMD.