At four different aquatic sites in Flanders (Belgium) with different types and degrees of contamination, juvenile carp (Cyprinus carpio) were exposed in cages for 4 weeks. After exposure, metals, polychlorinated biphenyls (PCBs), and selected organochlorine pesticides (OCPs) were analyzed in the tissues of the carp. Besides pollutant accumulation, several effects were measured as well. Condition measures such as changes in weight, condition factor (CF), and hepatosomatic index (HSI) were assessed. In addition, activity of acetylcholinesterase (AChE) and a set of blood biochemical parameters were measured. At all sites, accumulation of metals in the fish tissues was observed. Levels of cadmium and lead at some of the exposure sites were higher than the levels at the start and comparable to levels in fish from moderately metal-contaminated sites. For most organic pollutants, however, levels were not significantly higher than at the start. Only for two PCB congeners, levels had slightly increased but were still lower than levels in carp captured at noncontaminated sites. Although food limitation probably caused some of the observed effects, significant relationships were found between metal load in tissues and CF, AChE, plasma osmolality and HSI. This study shows that caged carp might be useful for the assessment of bioaccumulation and some effects of micropollutants in aquatic ecosystems.