For museum planning, optimum condition reference data for physical environmental variables is a basic determining aspect. The main physical environmental variables to be controlled are identified as air temperature and relative humidity for climate and illuminance and exposure time for lighting. Other physical environmental parameters are a main cause of deterioration phenomena, such as the air velocity around the object, the radiant temperature, the lighting source energy spectrum and the gaseous and pollutant concentration. To this aim a bibliographic search in the literature and in the technical recommendations was conducted. About 90 museum collections were examined in order to critically compare several references. As a result of the bibliographic search, suggested values for air temperature - relative humidity (climate) and illuminance - exposure time (lighting) were tranferred to diagrams.