Following the broad reform process applied in the public sector and due to the canghes occurred in the cultural and economical context, the assemblies and the regional councils are involved in the upholding of innovation and autonomy process also through the introduction of management methodologies aimed to the evaluation and control of their performances. The article synthesizes the elements of complexity typical of the performance concept applied to the regional legislative assemblies; it summarizes also the proposal of an explanatory model for the analysis of performances in legislative assemblies and in the regional council of Lazio. The framework’s utility in also linked to thfact that it could be used to identify which aspects of performance measurement system have been studied in deph and which ones have been not examined.