Twenty-one male Swiss albino mice were injected intraperitoneally with 2 x 10(5) Plasmodium berghei berghei-infected cells. Twenty-four mice were used as a noninfected control group. On the tenth day after infection, three mice were killed and the remainder were treated with chloroquine phosphate (0.025% solution) given orally. The dosage was subsequently adjusted to keep the parasitemia below 5%. Eighteen of the controls received the same chloroquine dosage. Diffuse proliferative glomerulonephritis was seen from day 10 of infection up to two months after treatment. Granular deposits of immune complex were seen in all glomeruli. At the end of third month and thereafter, all experimental mice were in a hyperimmune state, and the kidneys showed the characteristic of focal glomerulonephritis resembling some types of human focal glomerulonephritis.