Sporadic Parkinson's disease (PD) is a frequent neurodegenerative movement disorder. Both environmental and genetic factors have been studied in the etiology of PD. Among genetic factors, increasing evidences suggest that deletion/insertion (D/I) gene polymorphism of the angiotensin I-converting enzyme (ACE) may be involved in the pathogenesis of PD and in the occurrence of the adverse effects of chronic L-dopa therapy. We investigated this hypothesis by evaluating the frequency of the ACE gene D/I polymorphism in 120 Italian PD patients and 132 controls. Out of the 120 PD patients, 91 were under chronic L-dopa treatment. Our results revealed no difference in ACE I/D genotype (chi(2)=0.79, p=0.66) and allele (chi(2)=0.34, p=0.56) frequencies between PD and controls. We also failed to observe any significant association with the occurrence of L-dopa-induced adverse effects in long-term treated PD patients, thereby excluding the presence of an association between ACE I/D genotypes and the genetic susceptibility to PD and the development of adverse effect of chronic L-dopa therapy.