The purpose of this study was to investigate physical activity levels, stages of change, awareness, and differences in psychological factors relating to physical activity in an adult Dutch population, in order to identify specific objectives for physical activity promotion. Physical activity levels, self-rated physical activity, stages of change, awareness, attitudes, social influences and self-efficacy relating to physical activity were assessed among a random sample of 2608 adults using structured questionnaires. Almost 60% of the respondents did not meet the recommended target for physical activity to promote health. Half of these respondents were in the pre-contemplation stage, and >60% were overestimating their physical activity level. Furthermore, respondents who were not aware of their inadequate physical activity level had a less positive intention to increase their level of physical activity than those who rated their own physical activity level as low. Respondents in the pre-contemplation and maintenance stages had a less positive attitude, perceived less social support and had lower self-efficacy expectations towards increasing physical activity than those in the contemplation, preparation and action stages. The results suggest that interventions aimed at increasing physical activity in the studied population should be aimed at increasing awareness of personal activity levels and should be stage-matched.