Vibration of rings of isolated canine saphenous arteries depressed contractions induced by potassium chloride, prostaglandin F2 alpha, and activation of the adrenergic nerve endings by electrical stimulation. Peak contractions to exogenous norepinephrine were not significantly affected by vibration, being augmented, unchanged, or depressed, whereas contractions during the stable plateau phase were depressed. The calcium entry blocker diltiazem reduced the peak response but not the stable plateau phase of the contraction to norepinephrine; in the presence of diltiazem, vibration still depressed the latter. When vibration was applied during the steady state of contractions evoked by electrical stimulation, the depression was immediate, and its extent increased with both the amplitude (0.025-0.10 mm) and the frequency (30-150 Hz) of vibration. In arteries labeled with [3H]norepinephrine, vibration (120 Hz, 0.1 mm amplitude) during electrical stimulation induced a slight but significant increase in the release of labeled transmitter. It is suggested that the depression of contractions to potassium ions, prostaglandin F2 alpha, sympathetic nerve stimulation, and the plateau phase of the response to exogenous norepinephrine are caused by vibration depressing the force-generating process in vascular smooth muscle. Failure of vibration to significantly depress the peak contraction to norepinephrine may be explained by the facilitation by vibration of the influx of extracellular calcium ions.