The pathophysiology and pathogensis of malabsorption are presented. Investigation methods, including screening tests, fecal chymotrypsin estimation, lactose intolerance test, D-xylose absorption excretion test, blood tests for deficiency of nutrients, X-ray examination of abdomen, pancreatic imaging, ultrasound diagnosis, computed tomography, endoscopic retrograde pancreaticography, exocrine pancreatic function test, secretin cholecystokinin stimulation test and tubeless test are described. Treatment is discussed.