PicoQuant GmbH offers FluoFit, its multiexponential fluorescence decay fit software for Windows 95/98 and NT. FluoFit implements an iterative reconvolution of the instrument's response and the observed decay. The software uses nonlinear error minimization based on the Levenberg-Marquardt and Simplex algorithm, and a robust guess algorithm speeds convergence with few iterations. Up to three exponential decay models can be fitted to the observed data. Fit parameters include instrument response function, decay background and time shift.