Dichlorobenzamil, phenamil and other amiloride analogs (1–100 μM) elicit transient tension in rabbit skinned muscle fibers. Tension requires preloading of Ca 2+ into the sarcoplasmic reticulum, is facilitated by low-[Mg 2+] solutions, abolished by ruthenium red or by functional disruption of the sarcoplasmic reticulum, and is followed by inhibition of the caffeine-evoked tension. Bilayer recording of Cs + currents through the sarcoplasmic reticulum Ca 2+ release channel reveals that phenamil (10–100 μM) increases the open channel probability, whereas dichlorobenzamil affects the channel activity in a complex concentration- and time-dependent manner: stimulation occurs throughout exposure to 10 μM, but is followed by channel blockade when 100 μM dichlorobenzamil is used. It is concluded that stimulation of the sarcoplasmic reticulum Ca 2+ release channel accounts for the dichlorobenzamil- or phenamil-induced tension in skinned fibers, whereas depletion of sarcoplasmic reticulum Ca 2+ stores and channel block (with dichlorobenzamil) explains the inhibition of the caffeine-evoked tension by amiloride analogs.