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. Eggs of silver salmon (O. kisutch) were similarly treated. At an intensity of 157 foot‐candles all eggs died before hatching and at 86 foot‐candles 26.5 percent of the eggs and resulting larvae were dead by the time of first feeding. The control group had a mortality of 9 percent at the time of complete yolk‐sac absorption. No difference was noted in size or activity of larvae produced from eggs incubated in light or near‐darkness. As with the chinook eggs, an increase in light intensity decreased the number of temperature units required for hatching.