OBJECTIVES: The objective of the study was to clarify the relationship between major subjective symptoms and autonomic nervous system function by power spectral analysis of heart rate variability (HRV). METHODS: Short-term HRV was examined for 413 male workers in a Japanese information service company aged 19-45 years, and questionnaire survey on subjective symptoms and biochemical measurements were conducted at annual health checkup. RESULTS: The most prevalent subjective symptom (> or =10%) was dullness, followed by fatigue, backache, diarrhea, sleep disorder, and irritation. HRV in high frequency (HF 0.15-0.40 Hz) bands and the coefficient of variance in the electrocardiographic R-R interval (CVrr) were lower in the subjects with any of these six symptoms than in those without the symptoms. Both parameters were negatively associated with the reporting of any of the six symptoms by multiple regression analyses, controlling for the significant effects of age (HF and CVrr) and plasma cortisol levels (HF). CONCLUSION: It was suggested that the reporting of the subjective symptoms is one of good predictors for reduced parasympathetic tones.