The impact of health insurance with inequitable rituximab coverage on the survival of patients with diffuse large B-cell lymphoma (DLBCL) has never been reported. We conducted a nationwide multicenter analysis on the outcome of 553 adult patients consecutively diagnosed with DLBCL between July 2003 and June 2006, in whom treatment cost was reimbursed under the Civil Servant Medical Benefit Scheme (CSMBS) (n =201) or the Universal Coverage Scheme (UCS) (n =352). The international prognostic index was comparable between the two payment groups. Rituximab-based therapy was administered in 45.3% and 3.1% of CSMBS and UCS patients, respectively (p <0.001). With a median follow-up of 24.6 months, the 6-year progression-free survival (PFS) was superior for CSMBS patients (34.2 vs. 23.2%, p =0.005). "Not treated with rituximab-based therapy" was the strongest adverse prognostic feature indicating a short PFS (hazard ratio 2.1, p <0.001). It is concluded that lack of access to rituximab is the principal factor accounting for the inferior PFS observed in Thai patients with DLBCL who are treated under the UCS.