Children with malarial infection, due to P. Vivax and P. falciparum, were tested for cell mediated immunity (CMI) by lymphocyte proliferative response to mitogens PHA (phytohaemagglutinin) and PWM (poke weed mitogen) and antigen PPD (purified protein derivative). This was done during the period of parasitemia and after treatment, and compared to 19 normal matched controls. There was no significant difference between the patients and the control group with regard to PHA (patients 57.4 +/- 50.5; controls 61.3 +/- 54.9); PWM (patients 27.4 +/- 19.9, controls 29.9 +/- 24.5); PPD (patients 2.2 +/- 1.2, controls 1.9 +/- 1.4). There was also no significant difference in the lymphocyte responses during the period of parasitemia and after treatment. Hence, there does not seem to be any depression of CMI as shown by lymphocyte proliferative responses during childhood malaria.