This study focused on the relationship between the asymmetry of initial motor symptoms of Parkinson's disease (PD) and premorbid handedness of patients. Structural equation modeling has been used for this purpose. The survey consisting of validated items measuring handedness and questions related to side of occurrence of initial symptoms was administered to 472 patients with PD [277 men, 195 women, mean age 66.5 (9.3), mean duration of the disease 10 (6.1) years]. The unidimensional model of handedness fits the data well (chi(2) = 37.86, df = 20, P = 0.009, Root Mean Square Error of Approximation = 0.044, Comparative Fit Index = 1.00, Standardized Root Mean Square Residual = 0.042) and side of initial motor symptoms is not significantly related to the factor of handedness (r =0.11, SE = 0.07, P = 0.14). In contrast to several other studies, the results indicate that the side of first occurrence of PD signs cannot be predicted from premorbid handedness of patients.