The paper presents a study on biodegradation of carbendazim (1 mg/l) by homogeneous cultures of epiphytic (n = 25) and neustonic (n = 25) bacteria and heterogeneous (n = 1) cultures containing a mixture of 25 bacterial strains isolated from epidermis of the Common Reed (Phragmites australis, (Cav.) Trin. ex Steud.) and surface microlayer (SM approximately 250 microm) of eutrophic lake Chełmzyńskie. Results indicate that epiphytic bacteria are characterized by higher average capacity to decompose carbendazim than neustonic bacteria (p < 0.05). The half-life ofcarbendazim in epiphytic bacterial cultures equaled an average of 60 days. In the same period, neustonic bacteria reduced the concentration of the fungicide by 31%. The level of carbendazim biodegradation in mixed cultures of epiphytic and neustonic bacteria after 20-day incubation was lower than the biodegradation level in homogeneous cultures. Sixty-day homogeneous cultures of epiphytic and neustonic bacteria were characterized by a higher mean level of carbendazim biodegradation than mixed cultures. After 40-day incubation, mean values of biodegradation of the fungicide in homogeneous and mixed cultures were similar. It was demonstrated that among epiphytic bacteria, Pseudomonas luteola was the most efficient organism in reducing the concentration of carbendazim. Among neustonic bacteria, Burkholderia cepacia and Aeromonas hydrophila were the most effective in degradation of the fungicide.