Abstract: Objective To investigate the photographic distribution of anti-P-gp monoclonal antibody PHMA02 in nude mice transplanted with K562/A02 cell tumor.Methods PHMA02 were prepared by hy-bridoma technique, sodium dodecyl sulfate-polyacrylamide gel electrophorsis and Western-blot were used to analyzed its purity, fluorescence-activated cell sorting(FACS) was also used to determine its binding with K562 and K562/A02 cells. Nude mice were injected i.v with ¹²⁵I labeled PHMA02, and were scanned on dif-ferent time by SPECT.Results The purity and binding affinity of PHMA02 were both satisfactory. On the second day from injection, radioactivity appeared in all tumor regions of the P-gp⁺(K562/A02) group nude mice, and intensified in the following days.Concludsion The photographic difference of PHMA02 distribu-tion between P-gp⁺(K562/A02) and P-gp^-(K562) group could specifically distinguish the P-gp⁺ tumor tissue.