In the recent years, in the water and soils of the Black Sea are found oil products, whose concentration exceeds the allowable standard by 3 times. Due to the limited works on studying the petroleum products’ impact on the sea fish juveniles, evaluating the effect of low concentrations of fuel oil and diesel oil (½ maximum permissible concentration (MPC), MPC – 0.05 ml/l and 2 MPC) on atherina larvae was seen as important. This object has already been successfully used in testing the domestic sewage and pesticides. Despite the fact that Atherinidae species are not commercially significant, they are active pelagic fish species of the coastal zone of the southern seas and an important object in the trophic chain of the coastal biocenosis. As a results of the proper experiments, as well as of the literature data, it was proved that the above allowed concentrations of oil products should be revised from the point of view of their safety for aquatic organisms. During three days, the survival of larvae decreased by more than 50%, after which all species (including controls) died in 4-5 days. A similar experiment with diesel oil and fuel oil, due to its greater toxicity, included a feeding factor. Atherina larvae consumed both cysts and branchiopod nauplii, however, on the third day their intestines were empty. This fact, as well as survival rates exceeding the control values, is probably part of the organism compensatory reaction in response to the toxicant presence. From a methodological point of view, it would be more correct to carry out even acute and short-term toxicological experiments with feeding, because they significantly influence the determination of toxicity of the environment or of a specific xenobiotic.