The available literature on the evaluation of diastolic function, the importance of diastolic dysfunction in congestive heart failure (CHF), and the effects of therapeutic agents on diastolic dysfunction are summarized. The normal cardiac cycle consists of two components: systole (contraction; ventricular emptying) and diastole (dilation; ventricular filling). Recent studies have shown that 30-40% of patients with CHF have normal systolic function; the majority of these patients have diastolic dysfunction as the underlying disorder. As a result, the role of diastolic dysfunction in CHF is currently an area of interest for researchers. The two primary causes of diastolic dysfunction are left ventricular hypertrophy and ischemic heart disease. Patients with CHF caused by diastolic dysfunction and patients with CHF caused by systolic dysfunction have nearly identical clinical presentations. Therapy with diuretics, vasodilators, angiotensin-converting-enzyme inhibitors, beta-agonists, the partial beta-agonist xamoterol, phosphodiesterase III inhibitors, or calcium-channel blockers may be beneficial in patients with diastolic dysfunction. Therapy with digitalis glycosides would be of no benefit, and could theoretically be detrimental, in patients with predominant diastolic dysfunction. Available data indicate that beta blockers have neither an important beneficial effect nor an important detrimental effect on diastolic function. Continued studies into diastolic dysfunction and the diastolic properties of agents that are used in the treatment of CHF should enhance the understanding of this clinical syndrome and the drugs used to treat it.