Suspended solids, petroleum hydrocarbons (C₁₄-C₂₈) (PH), benzo(a)pyrene (B(a)P), heavy metals (Pb, Cd, Zn, Cu, Hg), and pH were analyzed in storm water runoff samples collected at five sites in different areas of Vilnius city during three rain episodes in May-June, and at one site characterized by intensive traffic conditions during six rain episodes in May-October 2007. The concentration of xenobiotics investigated in samples was highly variable, depending on the sampling site and rainfall intensity. The evaluation of the toxicity of storm water runoff samples to rainbow trout was undertaken. Alterations of fish biological parameters (mean growth, white blood cell count) revealed significant differences in the toxic effects of storm water runoff samples depending on the runoff discharge point and chemical composition. The most significant decrease in the growth of rainbow trout fry was induced by storm water runoff, with the highest concentrations of benzo(a)pyrene and petroleum hydrocarbons.