A validation of two rating scales is presented. We first translated the Modified Overt Aggression Scale (MOAS) and the Nurses' Observation Scale for In-patient Evaluation (NOSIE), which cover different aspects of psychopathology, into Italian. We then tested their validity and reliability in terms of inter-rater and internal consistency. For validity, both cases and controls were included: for the MOAS we compared patients who were aggressive (cases) to those who were presumably non-aggressive (controls). For the NOSIE, cases were acute inpatients and controls were subjects with expected stable behaviour. The Brief Psychiatric Rating Scale (BPRS) was also administered to cases in order to test convergent validity. Either the NOSIE and/or MOAS scales were administered to 358 psychiatric inpatients. A subset of these patients (131 for the MOAS and 226 for the NOSIE) was also used to test the inter-rater reliability. Both scales showed good psychometric properties. The correlation coefficients between raters were much higher than 0.75 (for the NOSIE) or 0.90 (for the MOAS), while the discriminant power between cases and controls was confirmed for both scales and good concordance with BPRS was observed. The NOSIE showed good internal consistency for all domains except neatness. In general the MOAS showed better results than the NOSIE for all psychometric properties, although both scales are suitable for monitoring the behaviour and aggression of acute ward inpatients.