Objective. This article describes the development of educational materials for a Women, Infants, and Children (WIC)based randomized controlled trial of an intervention encouraging timely bottle weaning. Method. Following a systematic process to develop of patient education materials, messages were first tested in 4 focus groups with 26 caregivers of WIC toddlers aged 7 to 36 months of age at the 2 study sites. Following review and revision, the materials were retested in one-on-one nutritional counseling sessions with 10 clients at the WIC sites who met the studys eligibility criteria. Results. Materials development was an iterative process requiring several levels of input, review, and revision. Use of a systematic process guided by steps adapted from the health education literature was crucial in ensuring continuous feedback from stakeholders, experts, and priority populations and to develop an intervention instrument that met the needs and expectations of all groups. Conclusions and implications. The content, theoretical orientation, and format of the materials were influenced at every turn by feedback from frontline WIC nutritionists, WIC policy staff at the state level, and WIC clients. Development of effective, easy to use materials requires constant input from key stakeholders.