In this study the effect of single and concomitantly added n-6 or n-3 polyunsaturated fatty acids (PUFAs) was investigated on human prostate cells. Data obtained from the single fatty acids (FAs) experiments showed that except for oleic acid (OA), arachidonic (AA) and linoleic acid (LA), which had very little (less than 10% cells dead) effect on the cells, an increase in dead cells was observed at physiological concentrations of, eicosapentaenoic acid (EPA), gamma-linolenic acid (GLA) and alpha-linolenic acid (ALA). However, this was not the case when combining these acids at physiological concentrations. A slight increase in cell death was only obtained with three combinations of ALA, namely with AA, OA, or GLA. Other combinations with ALA, such as with LA or EPA, had respectively no effect on cell number or increased the cell number by causing less cells to die. Other PUFAs combinations tested, did not show the three groups mentioned with ALA, but only the last two types, namely, no effect, or a decrease in the amount of cell death. The latter might mean that the FA combination had stimulated the cells, since a decrease in the amount of dead cells was observed. Therefore, it is concluded that the characteristics of combined FAs may differ from single FAs, which may explain some controversies in the literature and in response to treatments.