The correlation of symptoms (SX) with major arrhythmias (ARS) occurring during 24-hour ambulatory monitoring (AM) was investigated in a goup of patients referred because of dizziness or syncope. Ninety-eight consecutive patients, ages 25 to 82, who had adequate diaries of activities and SX, wre included. The ARS considered to be major were ventricular and supraventricular ectopy grade 2, 3, and 4 (Lown classification), sinus arrest and block, atrioventricular block, and sinus bradycardia less than or equal to 40/minute. Although all patients were referred because of dizziness and/or syncope, only 41 (42%) had their symptoms during the recording period. The ARS were recorded in 63 (64%). There was no statistically significant difference in the incidence or in the type of ARS in the group with, and the group without, symptoms (x2 = 1.64). Of the 23 subjects with both major ARS and recorded SX, only two had SX and ARS occurring concomitantly. It is concluded that (1) this is a group with a high prevalence of major ARS, (2) there was correlation between major ARS recorded and SX reported in a very small percent of cases (2%), (3) treating the ARS in the others could not be expected to abolish the SX, and (4) the high cost of monitoring should be considered in this context.