Objective To discuss the relationship between echogenicity and fat content in renal tumor.Methods 52 renal tumors were examined with preoperative ultrasonography,all tumors were 3 cm in diameter or less.The tumor echogenicity was classified as echogenicity increasement type (including hyperechoic and slightly hyperechoic) and echogenicity decreasement type (hypoechoic).The relationship between echogenicity and adipose staining in tumor were analyzed.Results In 18 cases pathologically proved benign renal tumor,14(77.8 ％) of the tumors were hyperechoic and were angiomyolipoma(AMLs),4(22.2％) of the tumors were hypoechoic including 2 poor fat AMLs and 2 rare benign tumors,slightly hyperechoic case was not detected.In 34 cases malignant renal tumors,27(79.4％) of the tumors were slightly hyperechoic including 22 clear cell renal cell carcinomas (RCCAs) and 5 papillary RCCAs,7 (20.6％) of the tumors were hypoechoic including 2 clear cell RCCAs,3 papillary RCCAs and 2 chromophobe RCCAs.Hyperechoic case was not detected.The adipose staining of 41 cases of echogenicity increasement type was all positive,in the 11 cases of echogenicity decreasement type,9 tumors were adipose staining negative,while the other 2 tumors were positive,and there were statistically significant between two groups (P ＜0.05).Conclusions Echogenicity was obviously correlate with fat content in renal tumor.Tumors containing rich fat appear to be increased in echogenicity,tumors without fat content appear to be decreased in echogenicity.