Objective To investigate the value of kinetic features measured by computer-aided diagnosis (CAD)for breast MRI.Methods One hundred and sixty four lesions diagnosed pathologically by operation or biopsy comprised the analysis set.Automated lesion kinetic information from CADStream programs for breast MRI was identified.Three CAD variables were compared for benign and malignant lesions: initial phase peak enhancement (greatest percentage of signal intensity increase on first contrast enhanced sequence),delayed phase enhancement categorized by a single type of kinetics comprising the largest percentage of enhancement (washout,plateau,or persistent),and delayed phase enhancement categorized by single most suspicious type of kinetics (any washout ＞ any plateau ＞ any persistent).Morphological characteristics of breast lesions were described according to breast imaging and reporting data system (BI-RADS).Initial phase peak enhancement mean values between benign and malignant breast lesions were compared by using Wilcoxon rank-sum test,delayed phase enhancement categorized by a single type of kinetics comprising the largest percentage of enhancement or by single most suspicious type of kinetics between benign and malignant breast lesions were compared by using Chi-square test.Results There were 72 benign and 92 malignant breast lesions.A total of 123 (75.0％) mass lesions were identified,and the other 41 (25.0％) lesions showed no mass.Thirty lesions were BI-RADS-MRI 2,68 lesions were BI-RADS-MRI 3,43 lesions were BI-RADS-MRI 4,23 lesions were BI-RADS-MRI 5.Initial phase peak enhancement mean values of benign and malignant lesions were 237％ (69％ to 629％)and 336％ (86％ to 793％),respectively.There was no significant difference between benign and malignant lesions in initial peak enhancement mean value (Z =-1.626,P =0.104).Delayed phase enhancement categorized by single most suspicious type of kinetics (any washout ＞ any plateau ＞ any persistent) for benign and malignant lesions were 15,10,47 and 2,3,87 respectively.There was a significant difference between benign and malignant lesions (x2 =23.562,P =0.000).Initial peak enhancement value ＜ 100％ or ≥100％ were 5 and 67 for benign lesions,3 and 89 for malignant lesions,respectively.There was no significant difference between benign and malignant lesions at 100％ threshold (x2 =1.181,P =0.277).Delayed phase enhancement categorized by a single type of kinetics comprising the largest percentage of enhancement (washout,plateau,or persistent) for benign and malignant lesions were 48,6,18 and 47,15,30 respectively.There was no significant difference between benign and malignant lesions (x2 =4.496,P =0.106).Conclusions Of CAD kinetics analyzed,only delayed enhancement categorized by most suspicious type is helpful for the differentiation between benign and malignant lesions.However,there is significant overlap between initial peak enhancement at 100％ threshold or delayed kinetics categorized by largest percentage enhancement types of benign and malignant lesions,so lesion morphologic features should be considered.