Although paramphistomes have been known to occur in cattle and sheep in the British Isles for-many years little precise information on the incidence, distribution and degree of infection is available. The diagnosis, except in exceptional cases, can be made only post mortem, or by the detection of eggs in the faeces. Before undertaking an investigation into this problem it was necessary to devise a simple standard technique for the collection of eggs from cattle faeces, which would be practicable not only in the laboratory but also in the field. This done, it became desirable to know firstly, within what limits egg counts were reliable criteria on which to base estimates of the number of parasites present; secondly, what was the smallest number of parasites which could be detected by faecal examination; thirdly, how much variation occurred in egg-counts from week to week in the same animals; and fourthly, if there were any variation in counts made on faeces collected at different hours of the day.