Motor complications induced by levodopa (L-dopa) treatment in Parkinson's disease (PD) are not well documented in patients of Chinese ethnicity. We performed a cross-sectional study to investigate the prevalence of dyskinesias and motor fluctuations, and the factors determining their development, in a population of Chinese patients with PD. Among 137 patients with PD, 98 (71.5%) had received a L-dopa preparation. Motor fluctuations were found in 74.5% and dyskinesias in 77.6% of the 98 patients. Patients with dyskinesias were younger at onset of disease than those without. Patients with dyskinesias and motor fluctuations had significantly longer duration of PD and L-dopa treatment, higher daily doses of L-dopa, and higher scores in the 39-item Parkinson's Disease Questionnaire (PDQ-39), when compared to patients without motor complications. Among these factors, motor fluctuations were best predicted by duration of L-dopa treatment and dyskinesias by disease duration. We conclude that motor complications are closely related to disease and treatment parameters, especially the treatment and disease duration.