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The gastrointestinal tracts of 672 crossbred cattle were obtained from various abattoirs in Kiambu District, Kenya from August 1992 to July 1993, and examined for the presence of gastrointestinal nematodes. Eight nematode species were found in 583 (86.8%) of the animals. The nematodes were, in order of prevalence: Haemonchus placei (67.0%), Cooperia pectinata (53.0%), Cooperia punctata (41.7%), Oesophagostomum radiatum (38.4%), Trichostronglyus axei (24.3%), Nematodirus helvetianus (19.6%), Trichuris globulosa (9.7%) and Strongyloides papillosus (3.6%). The intensity of the nematode infection was moderate; the mean burden being less than 7000 worms. H. placei accounted, on average, for 52.3% of the total burden. The total burden was least during the dry seasons and increased gradually during the rainy seasons. Adult H. placei persisted in the host throughout the year and there was no indication of hypobiosis. The heaviest gastrointestinal worm burdens were detected in 1.5- to 3-year-old animals. These findings are discussed with regard to their relevance for strategic control of gastrointestinal nematodes in cattle.