The research, development and use of natural products as therapeutic agents, especially those derived from plants, have been increasing in recent years. There has been great deal of focus on the naturally occurring antispasmodic phytochemicals as potential therapy for cardiovascular diseases. Naturally occurring diterpenes exert several biological activities such as anti-inflammatory action, antimicrobial and antispasmodic activities. Several diterpenes have been shown to have pronounced cardiovascular effects, for example, grayanotoxin I produces positive inotropic responses, forskolin is a well-known activator of adenylate cyclase, eleganolone and 14-deoxyandrographolide exhibit vasorelaxant properties and marrubenol inhibits smooth muscle contraction by blocking L-type calcium channels. In the last few years, we have investigated the biological activity of kaurane and pimarane-type diterpenes, which are the main secondary metabolites isolated from the roots of Viguiera robusta and V. arenaria, respectively. These diterpenoids exhibit vasorelaxant action and inhibit the vascular contractility mainly by blocking extracellular Ca(2+) influx. Moreover, kaurane and pimarane-type diterpenes decreased mean arterial blood pressure in normotensive rats. Diterpenes likely fulfil the definition of a pharmacological preconditioning class of compounds and give hope for the therapeutic use in cardiovascular diseases. This article will review patents, structure-activity relationship, pharmacology, antihypertensive efficiency, and the vascular mechanisms underlying the effects of diterpenes. Careful examination of the cardiovascular effects exhibited by kaurane and pimarane-type diterpenes will be provided.