A time‐resolved spectral photometer, i.e., an instrument for simultaneously measuring intensity, time, and wavelength (I‐t‐&lgr;) is described. The ‘‘spectro‐streak’’ apparatus comprises a grating objective coupled to a commercial streak camera with 2‐ps resolution, a channel plate amplifier, a CCD camera, and a computer for data processing. The necessary calibration and correction procedures are discussed in detail; these are sweep nonlinearity correction, shading correction, geometric distortion correction, wavelength calibration, spectral intensity correction, and dispersion correction. The performance of the instrument is demonstrated with an example of current interest, the measurement of the solvatochromic dynamic Stokes shift of fluorescence from a charge‐transfer system in solution.