Background: Obesity is an increasingly serious public health problem on a global level. Morbid obesity is defined as a Body Mass Index (BMI) of 40 Kg/m2 or more or a BMI of 35 Kg/m2 or more with obesity related comorbidities. Morbid obesity is associated with an increased incidence of wide spectrum medical and surgical pathological problems. Objective: To clarify the relation between morbid obesity, rapid loss of weight after sleeve gastrectomy and gallstone formation and if there is a need for adding prophylactic cholecystectomy during sleeve gastrectomy to obtain the best possible results after surgery. Patients and Methods: A total number of 50 morbidly obese patients were included in the study from September 2018 to April 2019 (prospective study). All patients were treated at Surgery Department of Al-Azhar University Hospitals. Males and females were considered for inclusion. Results: In our study, five cases (10%) underwent simultaneous cholecystectomy (selective cholecystectomy) for their asymptomatic gall stones detected by routine pre-operative pelvi-abdominal ultrasound. Simultaneous cholecystectomy was associated by a significant increase in the operative time by about 36 minutes without effect on the post-operative morbidity or hospital stay compared with other patients with no gallstones. Conclusion: Sleeve Gastrectomy for morbidly obese patients was followed by gall bladder stones in only 6.2%. Therefore, prophylactic intra-operative cholecystectomy seems to be not indicated and should be replaced by short-term (3 months only) of oral ursodeoxycholec acid during the period of maximum weight loss.