The effect of aspirin, ibuprofen, and nimesulide the three nonsteroidal anti inflammatory drugs on cell growth of MCF-7 human malignant breast tumour cells was investigated. The results demonstrated that the drugs exerted a preferential cytotoxic effect on actively proliferating cells but to different extents. The inhibitory effect of aspirin i.e. acetyl salicylic acid was around two to four times more pronounced than those produced by the Ibuprofen and nimesulide. The IC50 obtained with aspirin was 5 μg/ml whereas those of Ibuprofen and nimesulide were 13.5 μg/ml and 28 μg/ml respectively. Further the inhibitory effects were dose and time dependent. These effect of acetyl salicylic acid appeared to arise from a clear antiproliferative shift towards a reduced percentage of cells at the S and G2/M phases, together with an increased percentage of cells at the G1 phase. Aspirin could be more effective on MCF-7 than K-562 erythroleukemic cells and also as an inclusion compound with the advantage of oral administration and a greater bioavailability of the compound. Using the Chick chorioallantoic membrane model, the aspirin loaded pellets release sufficient acetyl salicylic acid to produce vascular regression and inhibition of angiogenesis.