Solutions of a paraphenylene ethynylene copolymer simultaneously absorb three photons of intense near infrared radiation. When the polymer relaxes, it emits visible radiation which can be seen clearly by the naked eye. Intensity dependent transmission studies have been used to measure &agr;3, the three photon absorption coefficient. The value obtained for a 10−3M solution of the polymer is 10−22cm3 W−2, which is remarkably large in view of the low concentration employed. ©1995 American Institute of Physics.