Both m o r p h o l o g i c a l and e l e c t r o p h o r e t i c isozyme v a r i a t i o n were examined in cucumaria curata Cowles, 1907, a common intertidal h o l o t h u r i a n of the West Coast of North America. This species has also been d e s c r i b e d under the name c. p s e u d o c u r a ~ Deichmann, 1938. T h i r t e e n p o p u l a t i o n s were sampled. Spicule density, and shape, tentacle size and number of p a p i l l a e at the male gonopore were determined. Five of the populations were examined for v a r i a b i l i t y in 8 isozymes. Spicule densities varied between p o p u l a t i o n s by m o r e than an order of magnitude. The spicule shapes were the same for all p o p u l a t i o n s a l t h o u g h the ratios of the d i f f e r e n t types varied. No relationship was found b e t w e e n g e o g r a p h i c a l location or habitat and any of the morp h o l o g i c a l characters. No p o l y m o r p h i s m s or v a r i a t i o n between p o p u l a t i o n s were found in any of the 8 enzymes analyzed by electrophoresis. However, the m o r p h o l o g ical data indicate random d i f f e r e n t i a t i o n b e t w e e n populations. The data indicate the existence of only a single species and thus the name c. pseudocurata should be considered a synonym of c. cura~.