Spontaneous Parkinsonism (SP) in schizophrenia-related disorders is poorly characterized. The objective of this study was to examine the concordance and clinical validity of alternative definitions of SP in patients with nonaffective psychotic disorders. Two-hundred drug-naive patients with nonaffective psychotic disorders were examined for core parkinsonian signs, including bradykinesia, rigidity, and tremor, and diagnosed of SP according to the Simpson-Angus Scale (SAS) cutoff criterion, the UK Parkinson's disease brain bank (UKPDBB) criteria, the National Institute of Neurological Disorders and Stroke (NINDS) criteria, and criteria requiring the presence of all three core features (full syndrome criteria). Parkinsonian signs and criteria were examined in relation to a number of relevant clinical variables. The most frequent sign was rigidity (33.5%) followed by bradykinesia (16%) and tremor (12%). The prevalence rate of SP according to the SAS cutoff criterion, the UKPDBB criteria, the NINDS criteria for possible and probable SP, and the full syndrome criteria were 20.5, 13, 25.5, 18.5, and 4%, respectively. Bradykinesia was specifically related to negative symptoms, rigidity to neurological soft signs, and tremor to dyskinetic movements. The set of criteria showing more associations with clinical variables were the NINDS criteria for probable SP. Patients fulfilling these criteria had higher ratings for poor premorbid adjustment, negative symptoms, dyskinesia, neurological soft signs, and poor global treatment response than those without that diagnosis. The NINDS criteria for probable SP, i.e., presence of any two of the three core parkinsonian signs, seem to be the most suitable for clinical and research purposes.