The use of pharmaceuticals increases their presence in the environment where they can be present in aqueouse phase or bound to soil and sediment due to various physical-chemical properties. Once in the environment, pharamceuticals are subjected to different processes such as biodegradation, hydrolysis or photolysis. For pharmaceuticals that are not subject to biodegradation or hydrolysis, the most significant degradation route is direct and indirect photolysis. The result of these processes leads to a reduction in concentration of pharmaceuticals and the formation of new compounds that may be more or less stable and toxic compared to the initial molecule. Therefore, to prevent the negative effects to the environment and human health due to the presence of pharmaceuticals in the environemnt, it is important to investigate their environmental behavior. In this paper, the photolytic degradation of antimalarium pharmaceutical hydroxylchloroquine (HCQ) was tested in buffer solutions of different pH-values. Direct photolytic degradation of HCQ was tested by under artificial Sunlight in MilliQ water at pH-values 5, 7 and 8. Examination of indirect photolytic degradation of HCQ was carried out in natural waters and model wastewaters. Hydroxylchloroquine solutions (10 mg L^ˉ1) were prepared for this purpose in the model wastewater of the pharmaceutical industry, modeled municipal wastewater, river and sea water. In the investigated conditions it was found that photolytic degradation of HCQ followed the first order reaction with a coefficient of determination higher than 0.99. The samples were analysed using high performance liquid chromatography coupled to diode array detector. Values of reaction rate constants and half-life times vary depending on experimental conditions. The results of the research have shown that photolytic degradation was the fastest at higher pH values. In addition, photolytic degradation of HCQ was influenced by matrix composition; the faster degradation was obtained in river water, probably due to the presence of dissolved organic compounds.