Monitoring the activity of broilers is a potential way for determining gait score level at commercial farms. In this study, a fully automatic monitoring technique was developed to measure the activity of broiler chickens with different gait score levels We carried out two experiments in order to assess the relationship between gait scores obtained by human experts and activity levels quantified by an automatic image monitoring system. The chickens were scored for their degree of lameness by experts according to the method of Kestin et al. (1992). For each experiment, a total of 30 birds, on day 32 were selected from a local commercial farm Five birds were selected in each of six gait score groups (GSO-GS5) The activity levels were obtained for all gait scores by using an automatic image monitoring system For this purpose, video surveillance images of broilers with six different predefined gait scores were analysed. In both experiments, there was a significant relation between gait score by experts and activity monitored by image analysis. The broilers with gait score 3 (GS3) showed significantly higher activities than the other gait scores in both experiments (P < 0.05), possibly due to their need for more feed. In both experiment, GS4 and GS5 showed significantly lower activities (P < 0 05). Overall, the results show that automatic camera monitoring system can provide an automatic tool in determination the activity in relation to gait score. This activity information can be used further to identify the effects of gait score on broiler behaviour. (C) 2010 Elsevier B V All rights reserved.