We report psychometric results of the Behavioural Activity Rating Scale (BARS) using data from three Phase III clinical trials of intramuscular ziprasidone in acutely agitated patients with psychosis (Studies 1 and 2) or in stable psychotic patients (Study 3). Convergent validity and divergent validity were assessed with baseline data from Studies 1 and 2 in subjects with acute agitation. To investigate convergent validity, we sought Pearson and Spearman correlation of BARS scores with scores on the Clinical Global Impression of Severity (CGI-S) Scale and a predefined cluster of agitation-related items from the Positive and Negative Syndrome Scale (PANSS). For divergent validity, we sought Pearson and Spearman correlation between BARS scores and a predefined cluster of PANSS items measuring negative symptoms. Discriminant validity was investigated with the help of subjects with moderate psychopathology (Study 3). Wilcoxon rank-sum and two-sample t tests determined whether mean (or median) BARS scores differed between subjects with acute agitation (Studies 1 and 2) and moderate psychopathology (Study 3). Responsiveness to treatment effect and rater reliability were also evaluated. In Study 2, Pearson correlation coefficients of BARS scores with PANSS agitation items and CGI-S were moderate (convergent validity) and statistically significant (P<0.005). The correlation between BARS scores and PANSS negative component scores was low (divergent validity). Treatment effect size was larger for BARS than for PANSS agitation items and CGI-S (responsive to treatment differences). Virtually perfect inter- and intra-rater reliability was achieved. Study 1 produced similar results. BARS showed psychometrically valid properties for measurement of behavioral activity in acutely agitated patients with psychosis.