Sexually transmitted infections (STIs) are the infections that can be transmitted from one sex partner, who already has such infection, to another. The causes of STIs in human are very well elucidated and their causative agents are identified as bacteria, parasites and viruses. The worldwide epidemiology of more than 20 types of STIs has been established, which includes diseases like Chlamydia, Gonorrhea, Genital herpes, HIV/ AIDS, HPV, Syphilis and Trichomoniasis. Though STIs affect both men and women indiscriminately, however, the pathophysiology of disease is more obvious among women. Other than abstinence, the most effective way to prevent the transmission or acquisition of STIs is to use a condom during sexual intercourse. Condoms are effective in decreasing the transmission of HIV. However, once contacted, STIs caused by bacteria or parasites can be treated with antibiotics. STIs caused by a virus may not virtually have any cure though the medicines may keep the disease under control. Correct usage of preventive measures greatly reduces but does not completely eliminate the risk of catching or spreading STIs.