Objective: Atopy is a condition of predisposition to allergic reaction to environmental allergens, and T cells have a critical role in initiating and ending allergic responses. This study was conducted to evaluate the T cell responses of atopic patients with allergic rhinitis who have allergen-hyperreactive memory CD4 T cells in vitro. Material and Methods: Cell surface markers (CD3, CD4, CD8, CD19, CD28, CD45RA, CD45RO, CD95, HLA-DR) were analyzed for T and B lymphocytes by flow cytometry using fluorescein isothiocyanate (FITC) or phycoerythrin (PE) labeled monoclonal antibodies. T cell proliferative response assessing pokeweed mitogen (PWM), tetanus toxoid (TT), purified protein derivative of mycobacterium (PPD) and cytomegalovirus antigen (CMV) were examined by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) reduction assay. Results: Immune profile and lymphoproliferative responses of 19 allergic rhinitis (AR) patients with positive prick skin test and nasal blockage, discharge, sneeze, nasal or ocular itching (mean age 33.2 +/- 8.4), and 10 healthy controls (mean age 31.6 +/- 9.1) were evaluated. CD3 and CD4 expression was higher in AR patients than in healthy controls. Memory (CD45RO) and activated (CD28) T cell levels were higher, but lymphoproliferation to PWM, TT, PPD, and CWV was decreased in AR patients. Conclusion: The high CD28 and CD45RO expression associated with atopy symptoms indicated that immune reactions in AR patients tended to show an undesirable shift toward Th2 skewed with high levels of allergen-reactive memory T cells. Consequently, the reduced lymphoproliferation to non-allergenic stimulants such as mitogens, bacterial and viral antigens in AR patients may lead to reduced immune response capability to infectious agents.