Medi-Cal-California's Medicaid program-underwent significant changes during the period 1978 through 1983. Most notable were the imposition of new copayments, reductions in physician reimbursement and selective contracting for hospital services. The state-funded medically indigent program was transferred to the counties and the state began to experiment with bulk purchasing of drugs and supplies, a lock-in for overutilizers and primary care case management. How have these changes affected primary care providers' participation in Medi-Cal? Surveys of California pediatricians in 1978 and 1983 suggest that while most continue to participate, the level of limited participation in Medi-Cal increased from 23% to 51%. Most pediatricians express discontent with the level of Medicaid payments and there is a growing sentiment that Medicaid regulations interfere with the provision of high quality medical care. Future Medi-Cal policy developments, such as contracting for physician services, should be structured in ways that maximize participation of primary care providers in the program.