Gene therapy is extremely promising in rheumatoid arthritis (RA). Electrotransfer (ET) is a recent method reported to enhance the in vivo effects of intra-muscular DNA injection. Interleukin-10 (IL-10) has anti-inflammatory effects in RA and in collagen-induced arthritis (CIA), a murine model of RA. We used ET to enhance penetration into skeletal muscle of plasmids encoding IL-10. CIA was induced in DBA/1 mice by immunization with bovine type II collagen. Injection into the tibial cranial muscle of low-dose (200 ng) pCOR plasmid encoding murine IL-10 (pCOR-CMV-mIL-10) was immediately followed by application of square-wave electric pulses (8 pulses of 200 V/cm, 20 ms duration at 2 Hz). Control groups received empty plasmid or saline before ET. When ET was performed twice on days 10 and 25 post-immunization, CIA was significantly delayed (P < 0.05) and attenuated (P < 0.001) in pCOR-CMV-mIL-10 ET groups vs. control groups. When pCOR-CMV-mIL-10 ET was started at disease onset (days 25 and 40), the clinical severity of CIA was reduced (P < 0.05). All groups treated early or late by pCOR-CMV-mIL-10 ET showed dramatic suppression of histological signs of arthritis compared to control groups. Taken together, these data indicate that administration of an anti-inflammatory gene by ET of naked DNA is effective in vivo in an arthritis model in preventive and curative protocols, even when low doses were given.