This study examined the extent to which significant changes after one year of a longitudinal, state-funded teacher professional development program were sustained during the second year. Participants taught in elementary schools located in small, rural school districts in the state of California in the United States. The research examined changes in early elementary teachers' science content knowledge; self-efficacy in teaching science; instructional practices in science; and contextual factors. Data sources included a teacher survey, self-efficacy assessment, content knowledge tests, interviews and classroom observations. Teachers experienced a significant increase in their knowledge of earth science in the second year. Their overall self-efficacy scores also increased significantly in the second year. Changes in instructional practices in science were largely sustained during the second year but were influenced by contextual factors such as resources, curricular demands, administrators' support and support from other teachers.