Nd2 is a murine monoclonal antibody of subclass IgG1 directed against purified mucin of human pancreatic cancer cell line SW1990. A previous biodistribution and radioimmunoimaging study of Nd2 demonstrated that the tumor accumulation rate of Nd2 was excellent and that apparently positive images of xenografts could be obtained using indium-111-labeled Nd2. In this study, I first investigated the biodistribution of F(ab')2 fragment on Nd2 on SW1990 bearing nude mice. I then tested the effects of intraperitoneally administered IFN-gamma on the rate of accumulation of Nd2 in the xenografts. F(ab') fragment of Nd2 showed more rapid maximal accumulation in the tumor and more urinary excretion in earlier period than whole Nd2. F(ab')2 fragment in the blood was lower in response more urinary excretion and tissue to blood ratio was therefore much higher than that of whole Nd2 at 12 hours and 1 day after administration. The biodistribution study to determine the effects of IFN-gamma on SW1990 bearing nude mice demonstrated that the accumulation rate of Nd2 in the tumor receiving intraperitoneal administration of IFN-gamma was significantly higher than that of control group. The results of these studies suggest that F(ab')2 fragment of Nd2 is useful in some respects in clinical use and that supplementary use of IFN-gamma may improve the rate of accumulation in the tumor.