Target-primaquine (TPQ)--the primaquine entrapped by galactosylneoglycoalbumin (G-NGA), was given intravenously (iv) to Wistar rats 2 h after sporozoite inoculation. The sporozoite viability (SPV) of TPQ 20 mg/kg group was revealed to be 1.2% 42 h after inoculation, which showed a decline of about 6% as compared to the control; besides, degeneration or retardation of development was present in 90% of EEF. In TPQ 10 mg/kg and PQ 20 mg/kg groups, the SPV were 2.8% and 5.0%, respectively, showing drops by 15% and 26% as compared with that of the control. Degeneration or retardation in development was also visible in about half of the EEF. In mice which were treated iv with TPQ 10 mg/kg or PQ 20 mg/kg 2 h after sporozoite inoculation, the prepatent periods were delayed markedly as compared with that of the control. Parasitemia did not appear in 2 mice in 10 mg/kg TPQ group further indicated the effectiveness of the drug. The results suggest that the anti-EEF effect of TPQ is apparently more promising than that of PQ.