The occurrence of certain complex forms of chronic ventricular arrhythmias or high frequency of less complex forms constitutes an independent risk factor for subsequent sudden death proportional to the degree of host organic heart disease. Currently, grade is probably best defined by referring to either simple or complex ventricular arrhythmias--complex forms being a combination of Lown's modified grades 3, 4, and 5, plus bigeminy. Frequency may provide an equally good expression of the information contained in gradation analysis, but one must recognize the potentially important transient advanced grades which may occur when overall frequency is low. The importance of such transient events has not yet been determined. The recently emphasized problem of spontaneous variation of frequency has yet to be resolved, both in terms of the patient who is not on drug therapy and those who are on long-term, steady-state therapy. For purposes of risk assessment for sudden death, until some of the controversies mentioned are resolved, the best compromise between accuracy, limitations, and economics remains the use of a single 24-hour Holter monitor analyzed for both frequency and the occurrence of complex or advanced grades. The goal of treatment should be a marked reduction or abolition of chronic VPDs, but if this is not successful, simply maintaining therapeutic blood levels of antiarrhythmic drugs may afford some protection against symptomatic or potentially lethal arrhythmias. The roles of provocative testing employing exercise, psychologic stressing, or electrophysiologic testing to identify high risk individuals are all being intensively investigated at the present time.