We have recently described a Plasmodium vivax-like human malaria parasite. The circumsporozoite protein of this parasite is identical to that of a simian malaria parasite, P. simiovale, but different from two known types of P. vivax. Here, we describe the production of two monoclonal antibodies, Pam 172 and Pam 135, specific for the circumsporozoite protein repeat sequence APGANQEGGAA of the P. vivax-like malaria parasite. These two monoclonal antibodies recognized air-dried sporozoites of P. simiovale but not other human, simian, or rodent malaria parasites tested.