The present study was carried out to identify the infective nematode larvae of cattle and sheep. Also, to differentiate some important nematodes infecting ruminants at the generic and species levels as a method helping for epidemiological studies. For this purpose, faecal samples were randomly collected from cattle and sheep, examined using standard floatation technique and positive samples with Strongyle type eggs were identified using coproculture. Identification of third stage larvae was based on the shape of the head, tail and sheath extending beyond it, size measurements of both larva and sheath (including; anus to tip of sheath and end of tail to tip of sheath). The morphometrical characters were studied for six 3^rd stage larvae of gastrointestinal nematode genera infecting cattle and sheep. Namely, Haemonchus, Ostertagia, Trichostrongylus, Cooperia, Oesophagostomum and Strongyloides. A key for the identification of these larvae is given and photographs are also provided to assist in their identification.