In the central Pacific, the nematodes Spirocamallanus istiblenni and S. monotaxis (Camallanidae) are common intestinal parasites of coral reef fishes. The 2 worm species are encountered in hosts in similar environments and are very similar morphologically. In recent published redescriptions, only 1 character was found to differ between the 2 species. Because that character had not previously been examined among worms of this family and because the original authors did not statistically test their results, the morphological data are here statistically reexamined for consistency with the differentiation between the 2 species. Both a discriminant function analysis and a hierarchical cluster analysis support the existing species designations based on morphological data. These analyses reaffirmed the conclusions of previous studies; i.e., the relative position of the male's second preanal papilla is the only diagnostic characteristic.