Experiments were undertaken to compare procedures for isolating Ascaris suum from mice. A standardised intragastric procedure for inoculation of A. suum eggs, which had a very low interdose variation (S.D.=6.2% of mean inoculation dose), was developed. There was no significant difference in the number of larvae recovered from the large intestine 4 h post inoculation (p.i.) by using either Baermannisation of washed intestinal wall or submucosal scrapings. In contrast, a significantly higher recovery of larvae was achieved by incubating the intestines vertically in a cylindrical saline- filled funnel. An agar-gel method was used to recover larvae from mucosal scrapings; however, the number of larvae recovered was the lowest of the methods tried. It was found that a significant increase in larval recovery from the liver at 24h p.i. resulted when the liver was pressed through a garlic press, rather than by using homogenisation. For lung recovery, the highest recovery of larvae (at day 8 p.i.) was obtained by disintegration of tissue with a pair of scissors and incorporating the tissue into agar-gel. The methods presented in this study may be useful for investigation of the histology, morphology and molecular biology of the early stages of A. suum.