Pythium regulare (CI-34) was isolated from some soil samples taken in the Canary Islands (Spain). This new species is very closely related to P. irregulare isolated from pea roots in the Netherlands by Buisman in 1927. The species of Pythium are members of the kingdom chromista. Pythium regulare is characterized by its ornamented oogonia bearing blunt or digitate spines, and its non-sporulating type of sporangia or hyphal bodies, its aplerotic oospores, its monoclinous and diclinous antheridia that at times crowd around the oogonia. The taxonomic description of this oomycete, the PCR of the internal transcribed region (spacers ITS1, ITS2, and the gene 5.8 S) of its ribosomal nuclear DNA as well as the nucleotide sequences, and its comparison with related species are given here.