Teaching Opportunities for Partners in Science (TOPS) is an outreach program using volunteers (the "partners") for: 1) assisting teachers in grades K-8 with preparation and delivery of science and engineering (S&E) lessons in the classroom; 2) providing content knowledge to teachers when needed to teach quality science and engineering lessons; 3) motivating students with career and educational models and information; and 4) educating families through after-school family science events. The outreach program began with partners who were retired scientists and engineers. Currently, the source of volunteers includes scientists and engineers who are employed or on leave as well as retired. The program began in 1993 at the San Joaquin County Office of Education, Stockton, CA, with three Partners at three elementary schools. The program now has 33 Partners at 32 schools in a five-county region in central California. Most partners volunteer to serve a minimum of a half-day per week during the school year; however, the schedule can be flexible to accommodate differing needs of the Partners. The partners attend a TOPS Institute during the summer preceding each school year. The Institute serves as a training course for new partners. This paper covers the history of the TOPS program, the selection and training of partners, the relationship between the partners and classroom teachers, development of lessons, comments from a partner and a classroom teacher, and the results of an evaluation of the program. (Contains 1 table and 3 figures.)