Recurrent acute tonsillitis is usually produced directly by micro-organisms, mainly beta-hemolytic streptococcus. Idiopathic tonsillar hypertrophy is presented without infection history and usually leads to obstructive sleep apnea. We have measured lymphocyte subsets in tonsillar cellular suspensions of infectious and obstructive tonsillar pathology by flow cytometry. Comparing with peripheral blood, the CD4+/CD8+ ratio for tonsillar pathology varies from 4.0 to 5.0 while in peripheral blood the ratio was 1.3. In tonsils the ratio of B lymphocytes/T lymphocytes is 1.6, being 0.3 in peripheral blood, cytotoxic T lymphocytes represent 8% in tonsils and 29% in peripheral blood, virgin or nonstimulated T lymphocytes (CD4+ CD62L+) consist of 3% in tonsils and 16% in peripheral blood. The immature B lymphocytes (CD20+ CD5+) represent 23% in tonsils and 12% in peripheral blood. In regards to NK cells (CD3- CD16+), 1% was found in tonsils and 11% in peripheral blood. In tonsils B lymphocytes and a low proportion of cytotoxic T lymphocytes predominate, in comparison to peripheral blood, with a CD4+/CD8+ ratio four times greater than tonsils. We have found in tonsils a significant increase of T cells (CD3+ and TCR alpha+ beta+) in infectious processes in comparison to obstructive pathology.