Nosocomial infections are infections acquired in hospital or healthcare service unit that first appear 48 hours or more after hospital admission or within 30 days after discharge following in-patient care. The main routes of transmission of nosocomial infections are contact, airborne, common vehicle and vector borne. Common infections are urinary tract infections (UTI), surgical and soft tissue infections, gastroenteritis, meningitis and respiratory infections. The agents that are usually involved in hospital acquired infections are Streptococcus sp., Acinetobacter sp., Enterococci, Pseudomonas aeruginosa, Coagulase negative Staphylococci, Staphylococcus aureus, Bacillus cereus, Legionella and Enterobacteriaceae family members including Proteus mirablis, Klebsiella pneumonia, Escherichia coli, Serratia marcescens. Out of these Enterococci, P. aeruginosa, S. aureus and E. coli have a major role. Various infection control programmes and organizations help to lower the risk of an infection during and after the period of hospitalization.