We report results from an experimental study that tested the effectiveness of dissemination interventions to improve implementation of smoking cessation guidelines in maternal and child public health clinics. We additionally examine individual clinic results for contextual explanations not apparent from the experimental findings alone. Twelve clinics in Illinois were randomized to three dissemination strategies: (i) core dissemination (provision of the 2000 Public Health System Clinical Practice Guideline and a tested smoking cessation program, including program supplies and training), (ii) core dissemination and access to telephone counseling and (iii) core dissemination, telephone counseling access and outreach visits to clinics. Implementation outcomes were post-dissemination improvements over baseline in the percent of smokers reporting receipt/exposure to (i) provider advice, (ii) self-help booklet, (iii) videos, (iv) posters and (v) an adjunct intervention. Results showed significant increases in the percent of smokers receiving a booklet (overall) and an adjunct intervention (Groups 2 and 3). There were no increases in smoker-reported provider advice or videos and poster exposure. Examination of individual clinic findings showed that seven clinics accounted for all the experimental effectiveness. Smoker-reported provider advice to quit also increased in these clinics. Type of clinic and the absence of disruptive events distinguished clinics with and without effective dissemination outcomes.