Background: Theobromine, an alkaloid naturally present in green tea, coffee, and cocoa, is known to possess properties of cardiac stimulation and antitussive effects. The aim of this study was to compare the pharmacokinetic (PK) characteristics of two different formulations (suspension and capsule) of theobromine in healthy male volunteers. Methods: A randomized, open-label, multiple-dosing, two-treatment, two-period, two-sequence, crossover study was conducted in Clinical Trials Center, Seoul National University Hospital with 12 healthy male volunteers. Subjects orally received either theobromine suspension 300 mg or capsule 300 mg twice daily for 4 days and crossover phases were separated by a 7-day washout period. Plasma samples were collected before dosing and up to 12 hr after the last administration. Plasma theobromine concentrations were determined by liquid chromatography-tandem mass spectrometry. PK parameters were estimated by a non-compartmental analysis. Results: Median time to peak concentration of theobromine suspension and capsule groups ere 0.33 and 2.50 hr, respectively. The mean [SD] values for peak concentaration at steady state ($C_{max,ss}$) and area under the plasma concentration-time curve during dosing interval at steady state ($AUC_{ au,ss}$) for suspension (13.90 [3.66] mg/L and 113.31 [31.95] $hr^*mg/L$) did not differ statistically from those of capsule (13.26[3.76] mg/L and 122.96[41.47] $hr^*mg/L$). The geometric mean ratios (90% confidence intervals) for suspension to capsule were 1.05 (0.95-1.16) for $C_{max,ss}$ and 0.92 (0.85-1.00) for $AUC_{ au,ss}$. Conclusion: These findings suggest that theobromine suspension 300 mg is similar to the corresponding dose of capsule 300 mg in terms of pharmacokinetic properties except the time to peak concentration at steady state.