Deviant workplace behaviours directed toward co-workers (harassment, intimidation, humiliation, scapegoating, undermining, sabotage, infighting, lying, verbal threats, malicious rumours) have negative effect on the social and psychological dimensions of any organisation and finally lead to the development of different organisational psychopathologies, although these individual behaviours are not seen as signs of psychopathology. Abusive behaviours are sometimes systemic and ingrained in the organisation culture, especially for those institutions characterised by a ’macho’ mentality (police, army). The purpose of the current study is twofold: (a) to analyse the psychometric properties of the Interpersonal Deviance Scale (DEVI Scale), an assessment tool developed by the psychologists of the Romanian Gendarmerie, and (b) to presents a strategy to optimise those characteristics. The 34 behaviours of the scale have been rated by two samples in two conditions (539 subjects used a 3-point rating scale and 238 subjects used a 5-point rating scale). Three criteria have been taking into account in data analysis: (1) item fit statistics for the Rasch model, (2) person and item reliability coefficients, (3) test information function. The preliminary results suggested that: (a) both types of rating scales fit the Rasch model, (b) the 3-point rating scale presents smaller values of person and item reliability (.65 - .96) and test information function (14), (c) the 5-point rating scale presents higher values of person and item reliability (.90 - .98) and test information function (25). The conclusion is that DEVI scale could be use in organisational diagnostic studies to assess the frequency of abusive behaviours.