20%) or diffusion conducted after the sixth day of the inoculation was inappropriate to the appearance of the precipitum. The positive rates of the precipitum in the group of serum of mice infected with P. berghei ANKA strain, and the group of serum of mice infected with the strain's chloroquine-resistant line were 73. 7% (28/39) and 86. 5% (32/37), respectively. The clearness and denseness of the precipitum in the two groups were increased during the period of 2nd to 6th day after infection of mice with malaria parasites. The positive rate of the control group (serum of normal mice) was 25. 6% (10/39), and the precipitum formed in the group was obscure (?) and remained the same from 2nd to 8th day. There was significant difference in positive rates between the experimental group and the control ( P

A 54-kDa protein overexpressed by chloroquine-resistant Plasmodium berghei ANKA strain was first reported by us. In this paper, the localization of this protein by immunoelec-tron microscopy is presented. The results showed that the protein was mainly scattered inside the cytoplasm of the early date trophozoites and schizonts of erythrocytic stage of P. berghei ANKA strain , and some of it was also found in cytoplasm of erythrocytes infected with parasites. The protein content was much higher in chloroquine-resistant P. berghei ANKA strain than in chloroquine-sensitive P. berghei ANKA strain, suggesting the importance of this protein in understanding mechanism of chloroquine resistance in malaria parasites .