The purposes of this study were to determine if hospitalized medical-surgical patients could be classified reliably according to their potential to adapt to stress; and to explore the relationship between their adaptive potential and length of hospital stay. Forty-six patients were selected for participation by use of a table of random numbers. Three classes of significantly different adaptive potential were identified: the Alarm and Impoverished states were considered as stress states, while the state of Equilibrium was considered a nonstress state. Although it was possible to distinguish stress from nonstress states, using only physiological parameters, psychological parameters were required to distinguish between the two stress states. The differentiation among the three coping states was used to predict subjects' potential for mobilizing adaptive resources. Length of hospitalization was then related to classification of adaptive potential.