The Professional Development Laboratory (P.D.L.) is a collaborative teacher development program in New York City which promotes collegiality and provides an environment in which new and experienced teachers can update skills, learn and practice new skills, and share classroom techniques with one another. Participants spent 3 to 4 weeks in the classrooms of experienced P.D.L. resident teachers while their classes were covered by adjunct teachers. Participants refined and updated their skills in such areas as classroom management, guided reading, whole language, positive disciplining, and teaching writing to limited-English-proficient/bilingual children. After the lab experience, follow-up visits to the participants' classrooms were arranged by the resident teachers. Participants shared their experiences with their colleagues by inviting them to observe their classes and by sharing information and materials. A total of 60 surveys were mailed, and about 15 teachers (25 percent) responded to the survey. Ninety-three percent of the responding teachers expressed satisfaction with the program. Participants reported making changes in their classroom management and structure, their teaching methodologies, and their attitudes. As a result, teachers noticed improvement in the learning environment and in their students' motivation, interest, and ability to work independently. Four recommendations for program expansion and improvement are offered. (JDD)