Although research on the role of social support in psychological well-being has increased, little attention has been given to behavioral methods for measuring these supportive mechanisms. To study the support exchanged in marital dyads, a behavioral observation system was designed and used to detect changes in the marital relationship of one white, middle class family participating in an Early Intervention parent training program. The behavioral observation system recorded supportive functions (cognitive guidance, social reinforcement, tangible assistance, socializing, and emotional support) at 30 second intervals as well as the directionality of the support. Observations were recorded during evening, home-based family interactions every 2 weeks for 5 months. Concurrent with the observed interaction periods, the parents proceeded through the parent training program from baseline to Intervention Level 3. An analysis of the results showed that it was possible both to monitor supportive behaviors reliably in a home setting, and to document changes in these behaviors. Changes in inter-parent support were found concurrent with involvement in the parent training program. Individual modification of dimensions of emotional support were also increased through the use of feedback and goal setting, as monitored by the observational system. (BL)