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<正>Species of the genera Toxocara and Toxascaris are common parasitic nematodes of dogs and cats, causing significant health problems. Toxocara canis is of known medical significance since its larvae are able to invade human tissues causing diseases such as ocular larva migrans (OLM) and visceral larva migrans (VLM). In the present study, based on the published sequences of the internal transcribed spacers (ITS) of ribosomal DNA (rDNA) of Toxocara canis, T. cati, T. malaysiensis and Toxascaris leonina, four species-specific forward primers were designed in the ITS-1 or ITS-2. With the common conserved reverse primer NC2 and the species-specific forward primers, ITS-1 and ITS-2 of rDNA were respectively amplified by PCR from 99 DNA samples representing four ascaridoid species from dogs and cats from China, Australia, Malaysia, England and Holland for the specific identification of these ascaridoid nematodes. The specificity tests indicated that there was no cross-reaction between these ascaridoids and T. vitulorum, Ascaris suum, Ascaridia galli and Anisakis simplex. The minimum detectable DNA concentrations of the specific assays were 0.14ng/μl for T. canis, 0.54ng/μl for T. cati, 0.38ng/μl for T. malaysiensis and 0.13ng/μl for Tα. Leonina, respectively. The sequencing results of the amplified specific partial ITS1 and ITS-2 fragments confirmed the validity of the specific PCR assays. These specific PCR assays could be applied to distinguish these ascaridoid species, and should provide a useful tool for the diagnosis and the epidemiology investigation of toxocariasis in humans.