  In recent years there has been considerable activity in using gamma-ray
bursts as cosmological probes for determining global cosmological parameters
complementing results from type Ia supernovae and other methods. This requires
a characteristics of the source to be a standard candle. We show that contrary
to earlier indications the accumulated data speak against this possibility.
Another method would be to use correlation between a distance dependent and a
distance independent variable to measure distance and determine cosmological
parameters as is done using Cepheid variables and to some extent Type Ia
supernovae. Many papers have dealt with the use of so called Amati relation,
first predicted by Lloyd, Petrosian and Mallozzi, or the Ghirlanda relation for
this purpose. We have argued that these procedure involve many unjustified
assumptions which if not true could invalidate the results. In particular, we
point out that many evolutionary effects can affect the final outcome. In
particular, we demonstrate that the existing data from Swift and other earlier
satellites show that the gamma-ray burst may have undergone luminosity
evolution. Similar evolution may be present for other variables such as the
peak photon energy of the total radiated energy. Another out come of our
analysis is determination of the luminosity function and the comoving rate
evolution of gamma-ray bursts which does not seem to agree with the cosmic star
formation rate. We caution however, that the above result are preliminary and
includes primarily the effect of detection threshold. Other selection effects,
perhaps less important than this, are also known to be present and must be
accounted for. We intend to address these issues in future publications.
