Stimulated four-photon mixing (SFPM) has been observed up to four orders in a 300-m-long, low-loss, large-core multimode silica fiber pumped by a dual-frequency dye laser. The phase-matching condition for SFPM was uncritically achieved in the multimode fiber, so that, by varying the frequency separation of the two laser lines, it was possible to tune continuously an intense line generated by SFPM under the Raman-gain curve in the range of 350 to 495 cm(-1).