To investigate the functional and immunological properties of the Ca-release channel in the sarcoplasmic reticulum(SR) of the eel skeletal muscle, [³H]ryanodine binding, SDS gel electrophoresis, ⁴⁵Ca release studies, and immunoblot assay were carried out in the SR of the eel skeletal muscle. Maximal binding sites(Bmax) and K_D values of [³H]ryanodine for Ca-release channel of the SR of the eel skeletal muscle were 19.44 ± 1.40 pmole/mg protein and 15.55 ± 1.69 nM, respectively. [³H]Ryanodine binding to RyR was increased by calcium and AMP. The SR of the eel skeletal muscle has two high molecular weight bands on the SDS PAGE. The mobility of upper band was more slower than the single band of the rabbit skeletal muscle, and that of the lower band was similar with the single band of canine cardiac muscle. Vesicular ⁴⁵Ca-release was activated by calcium. Ca-induced ⁴⁵Ca-release was significantly inhibited by MgCl₂(2 mM), ruthenium red(10 μM) or tetracaine(1 mM), but not by high concentration of calcium itself. AMP-induced ⁴⁵Ca-release was slightly occurred only in the absence of calcium, it was not inhibited by MgCl₂ or ruthenium red. Caffeine also increased ⁴⁵Ca-release from the SR vesicles, but it was not affected by MgCl₂ or ruthenium red. Polyclonal Ab against rat skeletal muscle RyR is reacted with that of rabbit, but not reacted with that of the eel skeletal muscle. These results suggested that ryanodine receptor of the SR of the eel skeletal muscle is showing some similar properties with that of mammalian skeletal muscle, but might be an another isotype channel having two bands which is less sensitive to AMP, not cross-reacted with antisera against rat RyR, and not inhibited by high concentration of calcium.