An imbalance between the Th1 and Th2 arms of the cellular immune system has been reported in several autoimmune diseases but not in chronic idiopathic urticaria (CIU). Peak, total secretion and secretory pattern of the Th1 cytokines (IFNγ and IL-2) and Th2 cytokines (IL-4 and IL-10) were determined in resting and stimulated peripheral blood mononuclear cells (PBMC) from nineteen CIU patients, six acute urticaria patients and twelve controls. Stimulated IL-4 secretion was significantly reduced in CIU patients as indicated by their five- and three-fold lower peak levels and total IL-4 secretion, respectively. The IL-4 secretory pattern overtime was also markedly different in patients and controls. The late secretion of IFNγ at 144h was also reduced in CIU patients. These aberrations were not detectable in AU patients. Secretion of IL-2 was lower in CIU and AU patients as compared to controls while IL-10 secretion was comparable in the three groups. Our data demonstrate for the first time a predominantly reduced IL-4 secretion in CIU patients. This is associated with reduced secretion of both IL-2 and IFNγ. These findings indicate a generalized down-regulation of both Th1 and Th2 cytokines' secretion in CIU.