Objective: To explore neurons with beta oscillatory activity in the subthalamic nucleus (STN) in relation to parkinsonian motor signs. Methods: We studied 27 patients with Parkinson's disease (PD) who underwent electrode implantation for STN deep brain stimulation. Thirteen patients were classified as akinetic-rigid (AR) type and 14 patients were classified as mixed type. Microelectrode recording was performed in the STN and the electromyogram (EMG) was simultaneously recorded. Single-unit and spectral analyses were performed. Coherence analysis was used to explore the relationship between beta oscillatory activity and EMG activity. Unpaired t-test and chi-square were used to compare the differences between the two PD types. Results: Of 130 neurons identified in the AR type, 43.8% were beta oscillatory neurons (mean: 21.3 +/- 6.87 Hz, beta FB) and 0.8% were tremor frequency oscillatory neurons (4-6 Hz, TFB). Of 102 neurons identified in the mixed type, 19.6% were beta oscillatory neurons and 26.5% were TFB oscillatory neurons. There was a significant difference in proportion of neurons with beta FB and TFB oscillations between the two PD groups. Additionally, 12% of the beta FB oscillatory neurons were coherent with limb EMG of the AR type, but there was no coherence in the mixed type. Most oscillatory neurons were localized in the dorsal portion of the STN. Conclusion: The STN beta FB oscillatory neurons correlate with parkinsonian rigidity-bradykinesia. The high proportion of beta FB oscillatory neurons found in the AR type of PD is indirect evidence for their importance in generating motor impairment.