Several detergents were investigated for their ability to increase activity of 2':3'-cyclic nucleotide 3'-phosphodiesterase in isolated myelin. The ability of Triton X-100 and Sulfobetaine DLH to solubilize the enzyme was also examined. Solubilization with Triton X-100 was only effective in the presence of salt, for example with NaCl 51% of the activity was solubilized. A single extraction with Sulfobetaine DLH yielded slightly more solubilized enzyme and did not require added salt. Both activation and solubilization of 2':3'-cyclic nucleotide 3'-phosphodiesterase appeared to be similarly dependent on detergent concentration, suggesting a common action of the detergent in the two processes. Myelin basic protein was solubilized more readily than the enzyme. In contrast with the enzyme in myelin, 2':3'-cyclic nucleotide 3'-phosphodiesterase activity in C6 cells was not increased in the presence of Triton X-100, and was partially solubilized by either Triton X-100 or NaCl alone. No myelin basic protein could be detected in C6 cells by radioimmunoassay.