As a result of complaints received from farmers as to the presence of parasitic worms in sheep, an attempt was made during the period October 1923 to September 1924 (inclusive) to ascertain the distribution and relative abundance of the more usual parasitic worms inhabiting the alimentary canal of sheep in North Wales. Regular collections were made from the following centres:—Pwllheli, Carnarvon, Bangor, Conway and Llandudno, with a few records also from Colwyn Bay, Bethesda, Menai Bridge and Denbigh. All the sheep examined were slaughtered for food purposes, practically the whole being obtained from slaughter houses. Almost all had grazed for considerable periods on the farms in the district mentioned, at elevations varying from sea level to 600 feet.