The phylogenetic relationships amongst Hammondia, Neospora and Toxoplasma w
ere investigated by DNA sequence comparisons of the D2/D3 domain of the lar
ge subunit ribosomal DNA and the internal transcribed spacer 1. The results
obtained allow us to reject the hypothesis that N. caninum and H. heydorni
are the same species and show that Hammondia hammondi is probably the sist
er taxon to Toxoplasma gondii.