1. Introduction -- 2. Traditional assessment and transdisciplinary play-based assessment: a comparison -- 3. Play, assessment, and transdisciplinary process: why each is important -- 4. Conducting the play session -- 5. Interpreting the observations and planning for intervention -- 6. Observation of cognitive development -- 7. Observation of social-emotional development -- 8. Observation of communication and language development -- 9. Observation of sensorimotor development -- 10. Rachel's TPBA -- 11. Parent involvement in the assessment process.