The purpose of the present study is to evaluate the clinical and diagnostic significance of incidental findings of renal and urinary tract abnormalities, and extraosseous uptake of bone scans. The authors analyzed bone scans using $^{99m}Tc-MDP$(methylene diphosphonate) in 1238 cases of bone disease from April, 1979 to March, 1981. The results obtained were as follows. 1. Total extraosseous abnormalities were 112 cases (9%), which include 64 cases (5%) of renal and urinary tract abnormalities and 48 case(4%) of other extraosseous uptakes. 2. Renal and urinary tract abnormalities were 32 cases(50%) of obstruction, 14 cases(22%) of nonvisualization, 6 cases of space occupying lesion in kidney, 8 cases of kidney displacement and 4 cases of urinary bladder deformities. 3. Other extraosseous uptakes were 16 cases (33%) of body fluid collection, 15 cases of tumor uptake, 9 cases of free pertechnetate uptake and 8 others.