Five Giardia isolates from primates and rodents were grown axenically and compared by different electrophoretic techniques. One isolate from a lemur (slow loris) contained a dsRNA virus also found in some of the Giardia of human origin. Using ethidium bromide stained gels and also Southern blots hybridized with a rDNA probe, two profiles of restriction fragment length polymorphism were found in the animal Giardia, which are identical to two profiles found previously in strains of human origin. Isoenzyme and total protein patterns obtained with agarose isoelectric focusing divided the strains in the same two groups. With pulsed field gradient gel electrophoresis, the isolates showed 6-8 chromosomal bands but none of the band patterns were identical. The size of the chromosomes varied from 0.8 to over 3.0 Mb. A ribosomal DNA probe hybridized with different bands.