A 131 bp long sequence comprising a fragment of the 5`untranslated region and a part of exon 2 of the insulin-like growth factor IGF 1 gene, originating from the dog (Canis familiaris), Chinese raccoon dog (Nyctereutes procyonoides procyonoides), red fox (Vulpes vulpes) and arctic fox (Alopex lagopus) were studied with the use of SSCP, RFLP and DNA sequencing techniques. The SSCP mobility shifts revealed an interspecies, but not intraspecies variability of this sequence. Detailed searching for point mutations was carried out by direct DNA sequencing of a 131 bp fragment of the IGF-I gene. Three silent point mutations at positions: 21 (A>G) in the arctic fox, 57 (T>C) in the red fox, arctic fox and Chinese raccoon dog, and 93 (C>T) in the red fox and arctic fox were identified, when compared with the dog sequence, respectively. Since the above mentioned mutations are detectable by the RFLP technique, DNA samples originating from the studied species can be easily recognized due to the presence of the species specific intragenic haplotypes.