We investigated the association between chronic carbon monoxide (CO) exposure and electrocardiographic maximum/minimum P-wave duration (Pmax/Pmin), P-wave dispersion (Pd), maximum/minimum QT interval (QTmax/QTmin), and QT and corrected QT dispersion (QTd/cQTd), which are known as predictors of atrial fibrillation, ventricular arrhythmias, and sudden death. We obtained electrocardiograms of 48 apparently healthy male indoor barbecue workers (age mean +/- SD; 33.6 +/- 9.4) who were working in various restaurants for at least 3 yr and 51 age-matched healthy men (age mean +/- SD; 35.1 +/- 6.7). Average working time of the indoor barbecue workers in their jobs was 15.6 +/- 7.1 yr. P-wave parameters were analyzable in 39 barbecue workers and 40 control subjects and QT intervals were analyzable in 44 barbecue workers and 47 control subjects. Clinical characteristics of indoor barbecue workers and the control group were comparable in terms of age, sex, body mass index, blood pressure, heart rate, Pmin, and QTmin. However, COHb levels, Pmax, Pd, QTmax, QTd, and cQTd measurements were higher in indoor barbecue workers than in the control group (6.48 +/- 1.43 vs. 2.19 +/- 1.30, p < .001; 106.15 +/- 7.47 vs. 101.50 +/- 6.62, p < .005; 30.51 +/- 7.59 vs. 24.50 +/- 6.77, p < .001; 406.59 +/- 17.64 vs. 390.85 +/- 13.15, P < .001; 48.40 +/- 8.87 vs. 34.89 +/- 5.85, P < .001; 53.64 +/- 9.14 vs. 37.77 +/- 6.71, P < .001, respectively). In Pearson correlation analysis there were significant correlations between COHb level and Pd, QTmax, QTd, and cQTd (r = .315 P < .005; r = .402, P < .001, r = .573, P < .001, r = .615, P < .001, respectively). In conclusion, the present study is the first to assess and find an association between chronic CO exposure and electrocardiographic Pd and QTd/cQTd.