This article describes the theoretical underpinnings, construction and
validation process of an instrument designed to measure developmental
processes in groups. A total of 164 employees of three health care fa
cilities comprised the validation sample. Reliability and internal con
sistency were assessed The process of establishing content concurrent,
criterion-related and construct validity ir also reported The results
support the reliability and validity of the Group Development Questio
nnaire. The existence of a dependable measure of group development may
stimulate more basic research of group development and may encourage
the creation of more research tools in this important area of study.