In Protozoan-type infections muscular and/or articular manifestations are not unusual. They are directly correlated to the presence of the parasite in the organism. In such cases a good diagnostic support can be given by the demonstration of the parasitic infection, the inefficacy of the classical therapy with FANS or steroids, and the good results obtained with a specific antiparasitic therapy. The most significant data that emerge from this description regard the possibility that when an arthritis or an arthralgia cannot be defined a parasitic infection has also to be excluded.