During the holy month of Ramadan, Muslims fast during daytime hours and restrict food and drink intake to the period after sunset.Two main meals are eaten during Ramadan, one before dawn (Suhur) and the other at sunset (Iftar).In diabetic patients, fasting may influence diabetes control and biochemical parameters.However, nothing is known about the effect of Ramadan fasting on insulin secretory efficiency. Aim Of The Study: to evaluate insulin secretory efficiency before and after Ramadan fasting in a sample of egyptian type 2 diabetic patients using proinsulin:insulin (PI/I) ratio. Patients and Methods: The present study included 44 type 2 diabetic patients either were fasting or not. Patients were classified into 3 groups: Group (A):8 Diabetic patients who did not fast the whole month. Group (B): 18 Diabetic patients who were fasting (18-22) days. Group (C): 18 Diabetic patients who were fasting the whole month. The Results showed:Significant weight gain after Ramadan fasting (P<0.05).There was significant decrease in PI/I ratio after fasting the whole month of Ramadan (P<0.05).There were significant positive correlations between PI/I ratio with fasting blood glucose (r= 0.811, P<0.05),weight gain(r=0.482,P<0.05) and HOMA IR(r= 0.417, P<0.05).There were significant negative correlations between PI/I ratio and the number of fasting days (r= -0.462, P<0.05) and HOMA B% (r=-0.346,P<0.05).There was highly significant negative correlation between fasting blood glucose and HOMA B% (r=-0.709,P<0.001). Conclusion: Reduction of PI/I ratio indicates the beneficial effect of fasting on β cell secretory efficiency and reduction of β cell stress especially in patients fasting the whole month of Ramadan .