Maspin, mammary serine protease inhibitor, is a recently identified tumour suppressor and has a profound effect on cell motility. This study examined the effect of gamma linolenic acid (GLA), an essential fatty acid (EFA) with anticancer properties, on the expression of maspin and motility of cancer cells. Six human cell lines including colon cancer, mammary cancer, and melanoma were used. Expression of maspin protein was determined by immunocytochemistry & Western blotting. Maspin mRNA was detected with reverse transcription-PCR (RT-PCR). Four of the six cell types expressed maspin with MDA MB 231 and ECV304 (endothelial cell) being negative. Treatment of these maspin positive cells with gamma linolenic acid (GLA) resulted in a concentration dependent stimulation of the expression of maspin protein with the effects seen as early as 4 hours. Linoleic acid had an inhibitory effects. Alpha linolenic acid and arachidonic acid had no significant effect. The mRNA levels from cells treated with GLA was seen to increase as shown by RT-PCR. Cell motility, monitored with time-lapse video recording and Hoffmann microscopy, showed a marked reduction in terms of spreading and migration on extracellular matrix coated surface. This reduction was reversed with anti-maspin antibody. It is concluded that GLA, a member of then-6 series of EFAs, up-regulates the expression of maspin which is associated with a reduction in the motility of cancer cells.