['To investigate the safety and efficacy of a dose-escalation regimen of trimethoprim-sulfamethoxazole (TMP/SMX) for prophylaxis against Pneumocystis jiroveci pneumonia (PCP) in rheumatic diseases.', 'Data from 41 patients, who received glucocorticoids with or without immunosuppressive agents and prophylactic use of TMP/SMX, were retrospectively analyzed. Thirteen patients were started on a daily dose of 10% of single-strength (SS) TMP/SMX, which was increased gradually (dose-escalation group), while 28 patients were started on 1 SS tablet daily (routine group).', 'In the dose-escalation group, the retention rate was 100% at 6 months. In the routine group, 5 patients discontinued TMP/SMX; the retention rate was 82.1%. Moreover, the retention rate when taking a daily dose of 50% or more of SS TMP/SMX, or 1 SS tablet thrice-weekly, was significantly higher in the dose-escalation group (100 versus 71.4%, P = 0.032). No PCP was observed in the dose-escalation group; however, 1 patient in the routine group, who had discontinued TMP/SMX, developed PCP. The rate of adverse effects was less, although nonsignificant, in the dose-escalation group (30.8 versus 46.4%, P = 0.344).'] Is a dose-escalation regimen of trimethoprim-sulfamethoxazole tolerable for prophylaxis against Pneumocystis jiroveci pneumonia in rheumatic diseases?