If policy makers and employers are to take health issues into account when making decisions that will impact on work practices and work environments, they will need accurate information concerning the impact change in psychosocial working conditions has on health status. Although research is increasing in this area, a variety of different methods have been used to define when change in work conditions has occurred. The present paper considers various issues related to the accurate assessment of change in psychosocial working conditions, focusing on research designs that involve the collection of data at baseline and a single follow-up time point. The aim is to inform investigators about these methodological issues so they can be considered in the design of studies, the analysis of data and the interpretation of research findings.