Aims: The purpose of this study was to evaluate the performance of the sequential application of ozonation and activated carbon processes in the elimination of water-soluble crude oil and thereby reducing total organic carbon (TOC) and toxicity for the rainbow trout larvae. Materials and Methods: A series of water-soluble fractions of crude oil, 5-100 ml/l, were prepared. Groups of ten rainbow trout fish larvae were exposed to the solution for 24, 48, and 96 hours. Toxicity (LC 50 : Median lethal concentration) and TOC tests were performed for the solutions before and after their treatment by sequential ozonation and activated carbon adsorption. Results: The LC 50 (96 hours) and TOC of the sample before the treatment process were 60 mg/l and 55 mg/l, respectively. After adsorption by 10 mg/l activated carbon, followed by ozonation with a concentration of 1 mg/l, the LC 50 increased to 145 mg/l and TOC reduced to 36 mg/l. Those values, after treatment with 30 mg/l activated carbon, followed by 7 mg/l ozone, reached 196 mg/l and 28 mg/l, respectively. In the experiment, ozonation by 1 mg/l ozone was applied, and then adsorption was carried out by 10 mg/l activated carbon, and the LC 50 was 149 and TOC was 35 mg/l. In the experiments with 7 mg/l ozone followed by 30 mg/l activated carbon, LC 50 reached 204 mg/l and TOC reduced to 28.5 mg/l. Conclusions: Primarily ozonation of crude oil polluted waters followed by adsorption by activated carbon can increase the removal efficiency of the process, which results in significant TOC and toxicity reduction.