Environmental effects of light. temperature, and pH of culture media on mycelial growth and fruit-body formation of Flammulina velutipes in synthetic media were investigated. Illumination inhibited mycelial growth, but illumination during the latter part of vegetative growth induced primordia formation- The optimum light intensity and exposure time were 100∼1000 lux and 4∼8 hours per day, respectively. High intensity of light was injurous, and in darkness primordia developed into very poor fruit-bodies. The optimum temperature was 25℃ for mycelial growth and 15℃ for fruit-body formation. The optimum pH range for mycelial growth was found to be from 5.0 to 7.0 and for fruit-body formation from 5.0 to 6.0. In low temperature treatments, a temperature of 15℃ was more effective than 5℃ or 10℃, it took about 12 hours for primordium formation, but at 5℃ or 10℃ about 48 hours. The most excellent fruit-body formation were produced from the mycelium growth for 7 to 10 days.