This study investigated the effects of co-administration of Na-EDTA and diminazene aceturate (DA) on the level of parasitaemia (LOP), parasite clearance, packed cell volume (PCV) and post-infection survival time (PIST) in mice infected with DA-resistant Trypanosoma brucei. Five groups of 10 mice were treated as follows: infected and treated with Na-EDTA+DA; infected and treated with DA alone; infected and treated with Na-EDTA alone; infected-untreated; and uninfected-untreated. The co-administration of Na-EDTA and DA led to reduced LOP and improvements in PCV (P<0.05), as compared with treatment with DA alone. Mice treated with Na-EDTA+DA had a marginally (P>0.05) higher PIST than did mice treated with DA alone. Comparison of the group given Na-EDTA alone with the infected-untreated group showed that the former group had a significantly lower (P<0.01) LOP, improved PCV (P<0.05) and higher (P<0.01) PIST. It was concluded that the co-administration of Na-EDTA and DA led to a slight potentiation of DA in the treatment of mice infected with DA-resistant T. brucei, and that the administration of Na-EDTA alone significantly enhanced the resistance of the infected mice.