Background/aim: In this study, we aimed to assess the clinical and immunological findings of our patients with common variable immunodeficiency (CVID). Materials and methods:We analyzed the records of 31 adult patients with CVID (12 females, 19 males). The patients were classified into clinical and immunophenotypic subgroups for statistical comparisons.Results: Our patients had some clinical signs in considerable frequencies, such as low body weight (45.2%), urinary tract infections (41.9%), various dermatoses (35.5%), and oral aphthae (32.3%). The histological findings in the biopsy specimens of the gastrointestinal tract (nodular lymphoid hyperplasia, villous atrophy, and lymphocytic infiltrates at mucosa) were significantly associated with splenomegaly, hepatomegaly, or low body weight (P = 0.005, 0.045, and 0.007, respectively). The patients with low CD4/CD8 ratios had lower IgG levels and a lower percentage of CD19+ B cells, but a higher percentage of activated T cells (P = 0.023, 0.011, and 0.028, respectively). Conclusion:In adults with CVID, there existed some clinical signs at considerable frequencies, but these are not overemphasized in the literature. The CD4/CD8 ratio is an important factor in antibody production and the clinical presentation of CVID. It seems that the adaptive immune system is on alert and subclinical immune activation insidiously continues in patients with CVID.