This two-phase evaluation documented the delivery and effectiveness of evidence-based health education methods by regular staff to pregnant smokers. During Phase 1, a total of 436 Medicaid patients were screened and 416 (95%) gave consent: 334 nonsmokers and 102 smokers. This historical Comparison (C) group was assessed to document the "normal" pretrial smoking prevalence, patient nondisclosure (deception), and cessation rates at the first prenatal visit and during care. After this study, a formative evaluation of SCRIPT methods was conducted among 139 experimental group patients and 126 control group patients. During Phase 2, a total of 6,514 patients were screened over a 36-month period: 1,736 (27%) were smokers and 1,340 (77%) gave consent. After randomization, 247 became ineligible. The remaining 1,093 smokers received brief routine advice to quit. The experimental group (n = 544) also received a "Commit to Quit" video, "A Pregnant Woman's Guide to Quit Smoking," and counseling. Self-reports and saliva were collected at baseline, greater than or equal to 60 days, and less than or equal to 90 days postpartum for cotinine analyses to document cessation and significant reduction (SR) rates. The Phase 1 formative evaluation documented a 24% nondisclosure rate at the onset of care. It also confirmed a significantly higher experimental (17.3%) versus control group (8.8%) cessation rate and experimental versus control group SR rates of 22% and 16%. During Phase 2, unplanned policy changes, and delivery of experimental group counseling procedures to 15% to 20% of control group patients, resulted in a final experimental group cessation rate of 12% and a control group rate of 10%. The experimental group SR rate of 18%, however, was significantly higher than the control group SR rate of 13%. Effectiveness varied by the stability of clinic infrastructure, and degree of fidelity of staff performance of assessment and intervention procedures. The methods and results of this study will assist future health education programs for pregnant smokers to plan and conduct process and impact evaluations in prenatal care. (Contains 4 tables.)