Eggs and resulting larvae of chinook salmon (Oncorhynchus tshawytscha) were exposed continuously to several intensities of fluorescent light (wavelength 3350 to 6000 A. with mean of 5800 A.) for a period extending from 24 hours after fertilization through absorption of the yolk-sac. At an intensity of 157 foot-candles all eggs died before the eyed stage; at 116 foot-candles all eggs died before hatching; and at 88 foot-candles mortality from premature hatching was as much as 35 percent higher than for controls incubated in near-darkness and receiving 0.02 foot-candles. Not more than 37 percent of the eggs exposed to 88 foot-candles hatched, compared to 74 percent for the controls. Most of the larvae of the 88 foot-candle group died by the time the yolk-sac was absorbed compared to a mortality of 30 percent by the controls during a similar period. Chinook salmon eggs under artificial light hatched sooner than those in near-darkness and the larvae from the light-reared group, when compared to the controls, were more sluggish, more darkly pigmented, smaller, and slower in absorbing their yolk-sacs. Of the two experimental lots of chinook eggs, one yellow- and one orange-colored, the yellow eggs hatched more quickly.