A patient-activated ambulatory electrocardiogram device with a solid-state memory loop was used to investigate 100 unselected patients experiencing palpitation, dizziness, or syncope. Clinically useful information was obtained in 68% of patients. Frequently, sinus rhythm had been restored by the time the patient activated the device, but the arrhythmia had been stored in the pre-event segment of the memory--a distinct advantage over many other patient-activated devices. This recorder is complementary to conventional 24 hour electrocardiographic monitoring in the investigation of possible arrhythmias and is particularly suitable for patients with infrequent symptoms. Because the stored data can be rapidly analysed by any commercially available electrocardiograph the device is suitable for use in district general hospitals.