Lameness, a common disease in crossbred dairy cows, badly affects their fertility. To elucidate, if estrous behavior, comprising of duration and expression of certain estrous behavioral sign(s) (EBS), is involved, an estrous expression score system was applied to objectively compare estrous behavior during 27 and 58 estrous periods, respectively, in 17 normal and 37 lame cows kept in a group of 200 cows under loose housing system in tropical India. The cows were detected in estrus and were closely watched daily for 30 min at 0630, 1030, 1430 and 1830 h from the beginning to the end of estrus. The duration of estrus was similar in the normal and the lame cows (18.7+/-1.2 h versus 17.2+/-0.9 h) and almost similar EBS were shown by two types of cows, albeit with varying frequency. Standing to be mounted, the highest ranking EBS was shown by equal proportions of the cows in both the groups (76.4% versus 73.0%). A lower proportion of lame cows showed head side mounting (35% versus 53%; P<0.05). The frequency of standing to be mounted events was lower in the lame than in the normal cows (2.4+/-0.4 versus 8.0+/-2.5; P<0.05). The lame cows earned non-significantly lower than normal estrous behavior score (1100+/-179 versus 1610+/-357). Further, the presence of more than one cow simultaneously in estrus enhanced the estrous behavior score in the normal (406.4+/-63.0 for one cow in estrus versus 793.0+/-146.0 for three cows simultaneously in estrus; P<0.05), but not in the lame cows. Lameness appeared to have suppressed the playful behavior during estrus probably owing to pain related stress. It is concluded that mildly lame cows appear to have normal physiological estrus. However, some of the EBS remain subdued which prone them to remain undetected for timely breeding.