Background. Evaluation of practical value of monitoring t(14;18) in peripheral blood in follicular lymphoma. Methods and Results. t(14;18) was tested in 115 follicular lymphoma patients by methods: FISH, nested and multiplex PCR of blood, bone marrow and lymph node specimens. We tested the patients with rearrangement MBR quantitatively by real-time PCR. Testing intervals of t(14;18) in peripheral blood were 1 month during treatment, 2–3 months during the first year after the end of treatment, then every 4 to 6 months. Patients were clinically examined in the same intervals and regular restaging was done by CT/PET. Each patient was evaluatee separately. Total detection of t(14;18) was 97 % regardless tissue and methods of detection, FISH was superior to PCR (95 % vs 72 %). The higher number of copies were observed in lymph nodes in comparison to bone marrow (p=0,036) and peripheral blood (p=0,016); 46/115 (40 %) patients were positive for MBR, we followed up behaviour of t(14;18) in peripheral blood in 33 of them in long intervals (>6 months, med. 33 months). Molecular and clinical courses correlated in 20/33 (61 %) patients, 7/33 (21 %) clinically relapsed in lasting molecular remission. We found very short interval to clinical relaps in 7 cases of molecular relapses (0–5 months, median 3 months). We could not define “threshold quantity” of clinically important molecular relaps. Lasting molecular remission was associated with clinical in about 60 % cases; lasting molecular activity corresponded with clinical relaps in 86 % patients. Conclusions. t(14;18) is highly associated with follicular lymphoma. In practice, monitoring of t(14;18) is feasible only in part of patients. Even if there is some correlation of clinical and molecular course, monitoring of t(14;18) in blood bears only limited prognostic value for the concrete patient. The treatment of patient can not be accomplished on the basis of these results only.

        Key words: follicullar lymphoma, t(14;18), bcl-2/IgH.