Intestinal parasites are common among labourers from foreign countries and in immigrants. Some worm-infections like ascaridiasis or enterobiasis occur in children quite often even in the cold climates. In cases of ascaridiasis only a heavy infection causes clinical symptoms. The diagnosis is made through the detection of eggs in the stools, as all the other worm-infections are diagnosed from the stool-test. Piperazine-derivatives are highly effective against ascaris; another useful drug is Pyrantel-Pamoate. Toxocara canis, which affects normally only dogs, can occur occasionally in humans. Its larvae migrate in the body and cause granulomas. The main clinical symptom of threadworms (enterobiasis) is itching around the anus. This parasite can be eradicated through Pyrvinium-Pamoate. The first symptom a patient notices in cases of taeniasis are proglottides--parts of the worms--which are passed with the stools. The drug of choice against all kinds of tapeworms is Niclosamide. Hookworms are rampant in tropical countries. Heavy infections can cause severe anemias, especially in children. Bephenium-Naphthoate and Bitoscanate are effective drugs against this parasite. The whipworm (Trichuris trichura) is very common in the warm countries. It can be treated by Tiabendazole and nowadays also with Mebendazole, which is virtually atoxic. Infections with Strongyloides stercoralis are difficult to eradicate, as there are different ways of reinfection. In case an infection with strongyloides is accompanied by other serious diseases cachexia and even fatal outcome has been seen.