Fry of three trout species; Black Sea trout (Salmo trutta labrax Pallas), rainbow trout (Oncorhynchus mykiss, Walbaum) and brook trout (Salvelinus fontmalis, Mitchill) were challenged by immersion with viral haemorrhagic septicaemia virus (VHSV) genotype le, originally isolated from whiting (Merlangius merlangus) in the Black Sea. The study was designed to determine and compare differences in their susceptibility to this isolate. VHSV caused mortality levels between 12 to 34% among the three trout species tested. The most susceptible species was Black Sea trout (cumulative mortality, CM = 34%), followed by rainbow trout (12%) and brook trout (12%) (chi(2)=16.7; P<0.05). In brief, VHSV genotype Ie was considerably virulent to the Black Sea trout, but also caused low levels of mortality in rainbow trout and brook trout.