 Occupational science evolved as a loosely organized effort by many scholars in different disciplines to understand human time use.It was named and given additional impetus in 1989 by a team of faculty at the University of Southern California (USC) led by Elizabeth Yerxa, who had been influenced by the work of graduate students under the supervision of Mary Reilly at the same university.Since its formal beginning at that time, which coincided with the establishment of a Ph.D. program in Occupational Science at USC; occupational science has evolved as an additional source of research to expand empirical knowledge underlying the profession of occupational therapy.