The aim of the work was to analyse the influence of storage conditions such as time and temperature on the stability of fluoxetine in biological material. Determination of fluoxetine in blood, urine and liver samples was carried out using the HPLC method. Analysis revealed that fluoxetine showed consistent stability in samples which were stored at –20°C. Fluoxetine was stable in biological material stored at +4°C and +25°C for a period of only one month.