Discrimination between salt fingering and turbulence-induced microstructure has been based upon horizontal wavenumber spectra of temperature or of conductivity. Information on probability distributions is discarded in such spectral analyses. We suggest that a discriminant may be found in probability distributions, namely that salt fingering is associated with marked suppression of kurtosis. This is demonstrated in records of towed microstructure from the eastern subtropical North Pacific. ¿American Geophysical Union 1987