Abstract. The dynamic systems approach provides a general framework for studying processes. Properties of that approach are applied to the issue of family assessment. The description covers methods of assessment of short-term processes (e.g., dyadic interaction) and long-term processes (e.g., changes in interaction patterns over years). Special attention is given to the meaning of fluctuation and its relation to transitions and changes of the family system's properties. Two examples of assessment methods and procedures are discussed. One concerns the use of state space representations, the other the design of family studies, encompassing the use of mathematical models of the hypothesized underlying processes.