Twenty-nine patients with a variety of connective tissue disorders were studied for the effects of immunosuppressive therapy on non-specific parameters of immune function. Baseline studies prior to therapy showed a frequent incidence of anergy (13%) lymphopenia (31%) and abnormal PHA response (43%). Despite these abnormalities in untreated patients it was possible to show an even higher incidence of anergy (31%), lymphopenia (66%) and abnormal PHA response (77%) following immunosuppressive treatment. The changes in lymphocyte count and PHA response were found to be statistically significant. It was found, paradoxically, that delayed hypersensitivity responses improved following institution of therapy in three patients. Clinical efficacy of immunosuppression correlated with lymphopenia and depressed PHA responses; in particular in the five patients with uncontrolled disease, these parameters were normal. Lymphocyte counts and PHA responses are the most simple and informative procedures to monitor immunosuppression in patients.