Robinson's xenic parasite culture method was used to investigate the prevalence of Dientamoeba fragilis and Blastocystis hominis in faecal samples submitted to the National Public Health Service for Wales (NPHS) laboratory at Aberystwyth. Culture, in combination with a commercial trichrome stain, gave a D. fragilis positivity-rate of 2.6% (25/976), and a B. hominis positivity-rate of 8.0% (78/976). Isolates of B. hominis and D. fragilis were typed using riboprinting of the amplified SSU rRNA gene. Sixty six B. hominis and thirty three D. fragilis isolates produced a product after amplification. The B. hominis typing results confirmed the extensive genetic variation reported by other workers, and six new ribodemes were found among the human isolates. Two animal Blastocystis isolates were typed; a monkey isolate was ribodeme 1, and an ovine isolate was a new ribotype. All D. fragilis isolates that were riboprinted were found to be genotype 1.