The Yakima First Steps Mobilization Project for Pregnant Substance Abusers, known as First Steps PLUS, is a demonstration project. The project seeks to improve the health outcomes of pregnant substance abusing women and their infants by enhancing existing perinatal services provided through Washington's First Steps Maternity Care Program and by integrating and coordinating maternity care services with comprehensive substance abuse intervention services. This interim report summarizes development of the project components, describes their implementation, and analyzes the outcome data available to date. The report emphasizes process evaluation, especially related to: (1) the creation and county-wide implementation of a screening tool to access risk of substance abuse among women receiving Medicaid as one component of community mobilization; and (2) completion of the continuum of care for treatment of chemical dependency through improved availability of treatment options. Process measures are described from the beginning of the project in July 1993 through December 1995. Outcome measures are presented for births which occurred between July 1993 and December 1994. Demographic characteristics, risk factors, and birth outcomes are compared for Medicaid and non-Medicaid women residents of Yakima and for Medicaid women who were and were not screened for risk of substance abuse. Appendices include a First Steps PLUS screening form and the diagnosis codes used in identification of substance abuse in the First Steps Database. (WJC)