The direct transfer of genetics materials into yeast cells Saccharomyces cereviciae as well as using of amylase, cellulase and Osmo gene(s) as gene(s) marker, for measuring the efficiency of transformations during the growth curve of the cells was investigated. A framework is developed for an adequate comparison of data obtained during different phases of growth. Results indicated that the exponential phase is the best phase of introduce DNA across the cell membrane. Whereas transformation percentage reached its peak at the end of exponential phase.                 Results also revealed that the transformation rates of cellulase expression gene(s) were lower than the transformation rates of α-amylase expression gene(s). These results might be due to the different regulatory genes with different locations which are proposed to explain the ability of producing the enzymes by the same yeast transformed isolates in a different rates.                 On the contrary, the high concentrations of NaCl decreased gradually the transformation percentage during the exponential period. On the other hand, no transformants can be obtained in the high concentrations of NaCl on the early exponential phase or stationary phase. This may due to a very low survival rates of cells.                 The greatest transformation rate which were recorded at the exponential phase (late exponential phase) in particular, may be attributed to the thickness of cell wall of yeast wall than other phases. The results concerning efficiency of transformants to express foreign genes did not only indicate possible transfer the foreign genes but are also instrument in developing a goal directed optimization strategy of the growth rate in the application of direct transformation technique.