This study compared several measures of cardiac perception and related them to patient' spontaneous reports of palpitations. One hundred and forty-five ambulatory patients referred for Holter monitoring for the evaluation of palpitations were compared with 70 asymptomatic nonpatients. Reports of palpitations during monitoring were compared with the ECG to determine whether they coincided with an arrhythmia. Subjects also completed a heartbeat detection task to determine whether they were accurately aware of cardiac systole while at rest. 20.7% of palpitation patients and 4.7% of asymptomatic controls demonstrated an accurate awareness of resting heartbeat (p = 0.01). Performance was unrelated to bodily amplification, somatization, hypochondriacal symptoms, ECG findings, or psychiatric morbidity. 34.3% of palpitation patients reported symptoms that consistently coincided with arrhythmias on ECG. These accurate patients had significantly lower levels of amplification, somatization, hypochondriacal symptoms, and psychiatric morbidity. Accuracy of symptom reporting and accuracy of heartbeat awareness were not statistically associated.(ABSTRACT TRUNCATED AT 250 WORDS)