The Structured Observation System (SOS) is a data collection method developed to document changes in the communication behaviours of children identified with speech and language delays. The system employs a rating scale which reflects the occurrence of communication behaviours as well as the amount of assistance needed for behaviours to occur. Pre- and post-treatment rating scores may be compared to measure changes in communication behaviours. The Structured Observation System is an effective, efficient and practical method to record clinical data. It was designed to be used frequently during a treatment programme and it may be adapted by others for the same purpose. The following are appended: (1) Description of structure and activities of the BELL programme; and (2) The Structured Observation System as used in the BELL Program at Butler University. (Contains 4 figures and 2 tables.)