In Ca2+- and Na+-deficient, isotonic 126 mM K+ medium, addition of 5 mM Mn2+ caused a tension about 2.5× greater than the tonic response induced by 126 mM K+ medium (Ca2+ 2.5 mM, Na+ 0 mM) in ileal muscle. When glycogen was depleted by incubation in a glucose-free, isotonic 126 mM K+ medium, addition of 5 mM Mn2+ induced only a very weak tension in Ca2+-free, isotonic 126 K+ medium. Phlorizin (10−3 M), a blocker of Na+-coupled glucose cotransporter and ouabain (9×10−5 M), an inhibitor of Na+, K+-ATPase, failed to inhibit the tension elicited by 5 mM Mn2+ in a Ca2+- and Na+-deficient, isotonic 126 mM K+ medium. Mn2+ was accumulated in the intracellular compartment in a Ca2+- and Na+-deficient, isotonic 126 mM K+ medium. The tissue ATP concentration was significantly reduced in a Na+-deficient 126 mM K+ medium. However, it recovered almost completely when 5 mM Mn2+ was added to the isotonic 126 mM K+ medium. These results suggest that the Mn2+-induced contraction in depolarized ileal longitudinal muscle in Na+-deficient medium may be maintained by a glucose transport which is not dependent on Na+ and insensitive to phlorizin.