Impairment of interferon (IFN) system in human immunodeficiency virus (HIV) infection and acquired immunodeficiency syndrome (AIDS) became a basis for searching IFN responses to monitor the disease progression. For detailed investigations 16 HIV+/AIDS patients with at least 4 successively taken blood samples available for IFN determinations were selected. IFN responses were tested in two ways. Firstly, IFN level in plasma was measured. Secondly, capacity of IFN production by leukocytes was evaluated. The latter was determined in the whole blood assay, in which Newcastle disease virus (NDV) and phytohemagglutinin (PHA) were used as IFN-alpha and IFN-gamma inducers, respectively. The levels of IFN induced in whole blood leukocytes varied considerably in all individuals that had been tested. Nevertheless, two patterns of IFN responses were observed. In pattern I, patients had low levels of IFN in plasma and high levels of induced IFN-alpha and IFN-gamma. It was characteristic for 8 patients in good clinical condition. On the contrary, severe disease found in 2 patients was correlated with high levels of IFN in plasma and low levels of induced IFNs (pattern II). In 6 patients IFN responses were classified as intermediate pattern I/II suggesting transition from pattern I to pattern II. A variation of pattern I was found in the case of a patient defined as long-term survivor having relatively low levels of all IFN tested. The results suggested that interferon measurements reflected clinical condition of HIV+ patients showing not only past but also current immune changes.