This study explored dimensions of adult reading motivation and collected reliability and validity information for a measure that assesses individual differences in adult reading motivation. Reading engagement theory provided the basis for an initial pool of items. A factor analysis showed that four dimensions, (a) reading as part of the self, (b) reading efficacy, (c) reading for recognition, and (d) reading to do well in other realms, accounted for a substantial amount of the variance in reading motivation. An overall reading motivation scale of 21 items with subscales representing the four dimensions was created using items with high factor loadings. The internal consistency of the total reading motivation scale was good and the internal consistencies of the subscales were reasonable. The total scale and subscales predicted reading enjoyment and time spent reading. A better understanding of adult reading motivation may aid those who support adult readers.