Concentrations of cefuzonam (CZON) in peripheral venous serum, uterine arterial serum and intrapelvic female organs of 29 women undergone simple total hysterectomy were determined by bioassay, using the cylinder-plate diffusion method. With an intravenous injection of CZON 1 g, the concentration at time 0 (Cp0) of peripheral venous serum and uterine arterial serum were 148.1 micrograms/ml and 155.4 micrograms/ml, respectively. Biological half-lives (T 1/2) of CZON were 1.07 hours in peripheral venous serum and 1.02 hours in uterine arterial serum. Concentrations in peripheral arterial serum were higher than 1.0 micrograms/ml at 4 hours after injection and remained at higher levels than minimal inhibitory concentrations necessary for most Escherichia coli strain for at least 4 hours. Concentrations of CZON in female organs were kept as high as peripheral venous serum, and ratios of CZON concentrations in uterine tube and endometrium to that in peripheral venous serum were 0.74 +/- 0.34 and 0.44 +/- 0.25, respectively. Since CZON is characterized by potent antibacterial activity and broad spectrum, it should be effective for infectious diseases of the female uro-genital tract.