Histamine accumulates in food via microbial decarboxylation of histidine. Small amounts of histamine naturally occurring in food under normal circumstances do not pose a public health hazard. Certain microbial species such as Enterobacteriaceae and Pseudomonas slip. have considerable capacity for histamine formation and can proliferate during handling or processing of foodstuffs, possibly elevating the histamine content to a harmful level. The objective of this study was to measure the formation of histamine and microbiological changes in fresh Chalcalburnus tarichi from Van lake and stored at 4 degrees C for up to 15 days. Fish muscle samples were taken on day 1, 3, 5. 7, 9 11, 13 and 15 of experiment, during storage. Histamine content was determined using a spectrofluorometric method and the total count and features of Enterobacteriaceae and Pseudomonas spp. present in the samples were established by standard microbiological procedures. The initial concentration of histamine was 27.5 mg/kg, increasing gradually up to 134.38 mg/kg on day 15. Total viable bacterial count varied from 8.0 x 10(2) to 9.0 x 10(9) cfu/g. Enterobacteriaceae was in the 2.0 x 10(2) to 6.5 x 10(9) cfu/g range, while Pseudomonas spp. was in the 3.0 x 10(2) to 7.3 x 10(9) cfu/g range.