The C-terminal domain of the alpha-toxin (cpa247–370) of Clostridium perfringens has been expressed in Escherichia coli and purified. Antiserum raised against cpa247–370 reacted in an identical manner to anti-alpha-toxin serum when used to map epitopes in the C-terminal domain, suggesting that cpa247–370 was immunologically and structurally identical to this region in the alpha-toxin. The isolated cpa247–370 was devoid of sphingomyelinase activity or haemolytic activity and was not cytotoxic for mouse lymphocytes. Haemolytic activity was detected when cpa247–370 was tested with the N-terminal domain of the alpha-toxin (cpa1–249), confirming that cpa247–370 confers haemolytic properties on the phospholipase C activity of the alpha-toxin. Haemolytic activity was not detected if cpa247–370 was tested with the Bacillus cereus phosphatidylcholine phospholipase C, nor if cpa1–249 and cpa247–370 were incubated sequentially with erythrocytes.