Sexually transmitted infections are infectious diseases that are transferred from an infected individual to a healthy one by sexual contact, and can also be transferred by an indirect contact from a mother to a child during birth. The prevalence of the sexually transmitted diseases in Croatia is tracked by mandatory case reporting as a part of epidemiological surveillance, as well as by case registration in the primary health care sector. Due to the ease of transfer, sexually transmitted infections are one of the most salient public health challenges in the world, with more than 440 million affected individuals every year, and most of them younger than 25 years of age. Sexually transmitted infections are caused by various microorganisms such as bacteria, viruses, fungi and parasites. When parasitic sexually transmitted infections are concerned, the most common ones are pubic lice, scabies and trichomoniasis. Pubic lice are caused by a parasite Pthirus pubis, which feeds exclusively by blood and lives on people. Sexual contact is the most common route of infection, but it is also transferred by bed sheets, clothes or towels. The pubic lice cause a strong itching irritation around the genitals, and can also affect the anus. Scabies is caused by a parasitic miteSarcoptesscabeiwhich lives on the human skin. It is easilytransferred from one individual to another by infected towels, bed sheets, physical contact, sexual intercourse – with a subsequent development of a strong itching sensation. Trichomoniasis is caused by Trichomonas vaginalis, a single-celled anaerobic protozoan parasite that causes infection of the genital system. The most common route of infection is by sexual contact,but it can also be transferred froma mother to a child during birth. In women it predominantly causes vaginitis characterized by a foamy yellow discharge and an itching irritation; conversely, men can beasymptomatic or present with urethritis. It is easily diagnosed and treated with antimicrobial agents. Complications that may arise are difficulties in establishing family and closeness. In order for the treatment to be successful after infection with a sexually transmitted agent, both of the partners have to be treated. Finally, education of young people has a big role in the prevention ofsexually transmitted diseases, but also early recognition of the symptoms and disease awareness.