  We re-examine the technique of determining the redshifts of galaxies from the
ratio of the submillimeter-to-radio continuum flux densities based on a
recently published catalog of 850~$\mu$m sources. We derived the expected
variation of this ratio as a function of redshift incorporating the expected
average luminosity and the spectral energy distribution (SED) of dust emission
and the radio continuum. We find that the existing data for most of the high
redshift ($z \gtsim 1$) sources correspond to our new calculation. Amongst the
well-identified sources, there is none with an index significantly higher than
predicted. Sources which have an index lower than predicted are either within
the error zone or much lower, the latter presumably having AGN-dominated
radio-continuum emission. We find the median redshift to be $\sim 2$, which is
consistent with that deduced by previous work ($\sim 3$) within the error. We
also discuss the various systematic effects that can affect the accuracy of the
redshift estimate. We examine other methods of redshift estimation, like
photometric ratio in the submillimeter and locating the peak of the SED in the
rest system of the objects. We conclude that while the various methods are
helpful in identifying high-redshift objects and making a crude estimate of the
redshift, they are not, at present, accurate enough for a detailed study of
redshift distribution of the submillimeter galaxies.
