low - Fat Gouda- like cheese (LFC) was manufactured under the Egyptian condition to study the effect of adding either Simples®-100, or microbial Transglutaminase (mTGase) to cheese milk on the gross chemical composition, fatty acids profile (FAP), microstructure and organoleptic properties of the resultant cheese, during 90 days of ripening. Eight treatments were made from cow's milk; one of these treatments served as control, 3±0.1% fat (C1). The other seven treatments were made from milk standardized to 1.5±0.1% fat, one of them served as control 2 (C2) and the three treatments were made with adding Simples®-100, at a rate of 0.2, 0.4 and 0.6 g/1 liter of milk, whereas the other three treatments were made with adding mTGase at a rate of 0.3 , 0.5 and 0.8 g/ 1 liter of milk. Results revealed that fat reduction in cheese milk, increasing the moisture, pH values, protein and salt on dry matter basis ( P/DM & S/DM ) ; and decreasing the cheese yield, acidity, fat on dry matter basis and cheese ripening indices in the resultant LFC , in fresh and ripened cheeses. It also affected the fatty acids profile by increasing the total saturated fatty acids (TSFA) and decreasing the total unsaturated fatty acids (TUSFA). The microstructure of LFC was characterized by considerably few vacuoles or voids, a more dense and extensive protein matrix, reducing the coalescence of fat globules, and translucent appearance. The addition of fat replacer (FR) or (mTGase) to cheese milk had an apparent effect on the chemical composition and yield; fatty acids profile; microstructure and organoleptic properties of the resultant LFC. So it increased the moisture, P/DM, acidity, cheese ripening indices and yield. Moreover, it increased the total of SFA and USFA in both fresh and ripened cheeses as well as the SFA / TFA ratios. There is a direct relationship between the level of FR or mTGaseadded and the concentrations of both SFA or USFA in fresh or ripened cheeses. FR or mTGase, furthermore, improved much the microstructure and organoleptic properties (especially its body & texture) of the resultant LFC.