One way to assess the impacts of toxicants on populations of anurans is through developmental stability (DS) - the ability to buffer stresses during development stages. To assess the extent of possible perturbations in DS of frogs that inhabit a polluted industrial area east of Plovdiv city, Bulgaria, we applied analysis of fluctuating asymmetry (FA) in ten morphological traits in P. ridibundus. As a control group, we used animals inhabiting a less disrupted site. Based on the FA levels obtained for the frogs from both sites, we evaluate the state of their habitat. In the contaminated site, the mean FAMI (frequency of asymmetric manifestation of an individual) index for P. ridibundus individuals was 0.87 and in the reference site, it was 0.37, respectively. In our opinion, these results are evidence that in the population inhabiting the industrial area, there are very serious disorders in DS. We believe that they are the result of the chronic effects of stress agents of anthropogenic origin, whose negative effects affect all stages of the life of individuals. The results show that changes in the levels of asymmetry in the meristic morphological features in adults and sexually mature individuals of P. ridibundus are a very reliable method for bioindication. [ABSTRACT FROM AUTHOR]