peer reviewed ; Viola calaminaria (Gingins) Lej. is a rare and threatened species, endemic to metalliferous soils in E Belgium, S Netherlands and W Germany. In order to provide basic information for a conservation strategy, we performed an ecogeographic survey of almost all V. calaminaria populations currently existing in Belgium. Twenty-four populations were found, distributed in three geographic groups all in the Province of Liège. The area covered by V. calaminaria ranged from < 1 m2 to 3.2 ha. The largest populations were found in sites contaminated by atmospheric deposits from metal smelters. Soils were extremely variable in heavy metal and nutrient concentrations, but concentrations of Zn, Pb and Cd were consistently higher than reference values for normal soils. V. calaminaria was most often found in association with other metallophyte and pseudometallophyte taxa typical of metalliferous sites. Plant communities identified by TWINSPAN analysis generally fitted the heavy metal associations previously described but two unusual heavy metal plant communities were identified. Based on a canonical correspondence analysis, pH was the only factor that was clearly correlated with the floristic composition of plant communities associated to V. calaminaria. This study confirmed the ecological endemic status of V. calaminaria and the importance of the conservation of metalliferous sites.