The value of personal norms (Schwartz, 1977) for proenvironmental behavior has been demonstrated in previous studies (e.g., Vining & Ebreo, 1992), but not in addition to the theory of planned behavior (Ajzen & Madden, 1986). In the present study, this combination was investigated by means of a mail survey among a sample of 305 Dutch citizens who were enlisted to participate in a behavioral change intervention program on environmentally relevant behavior. Personal norms appear to increase the proportion of explained variance in 5 intentions and 4 self-reported measures of performed environmentally relevant behaviors beyond that explained by three of the theory of planned behavior constructs (i.e., attitude, subjective norm, and perceived behavioral control). Issues evoked by these results are discussed.