Pathophysiology, clinical features, diagnosis and treatment of important specific infections like tuberculosis, leprosy, tetanus, syphilis and gonorrhoea are described. Dosage schedule of antitubercular drugs is outlined according to revised national tuberculosis control program. Causes and management of multiple drug resistance tuberculosis is described. Brief outline of hepatitis and HIV infection is given with special emphasis on universal precautions during surgery in HIV patients and procedure to be followed in case of contamination of surgeon with infected blood.