The SWT was performed on 30 patients with chronic haemolytic streptococcus maxillary sinusitis, and 5 controls with no streptococcus in their nose and throat. Foreign and patient's own organism were used as antigen. The lymphoblastic transformation was higher in control streptococcus free patients than in chronic maxillary sinusitis, more when using foreign than patient's own organism. The failure of cellular immune response as a contributary factor tochronicity of maxillary sinusitis is discussed. The possible value of prepared foreign streptococcus vaccine in prevention and treatment ismentioned.