Abstract
A strain of T. evansi was made drug-fast to quinapyramine, suramin, stilbamidine and tryparsamide, respectively by treating mice with gradually increasing subcurative doses, passage of the relapse strain, and so on. The resistance exhibited to neutral aromatic arsenicals, melaminyl compounds, derivatives of acridine, diamidine and phenanthridine, and quinapyramine and suramin was analysed.