The characteristics of new phosphors, comprising orthophosphates of calcium, strontium, and barium, and their mixtures are described. The primary (absorbing) activator is tin dissolved in the matrix and with this activator alone strontium, barium, and alpha calcium phosphate emit either in the long wave ultraviolet or the blue regions of the spectrum, while beta calcium phosphate emits mainly in the red. Introduction of manganese as a secondary activator into beta calcium phosphate or into the mixed calcium‐strontium phosphate gives deep red emission. Variable color can be obtained by varying the manganese content. Beta calcium phosphate, tin activated, has an efficiency of 45 lpw in 40 watt fluorescent lamps and their color is close to 3500° White. It gives outstandingly good color rendition and represents an improvement over the red phosphor now used in the Deluxe line of lamps.