  The ZEPLIN collaboration has recently published its first result presenting a
maximum sensitivity of $1.1 \times 10^{-6}$ picobarn for a WIMP mass of
$\approx$ 60 GeV. The analysis is based on a discrimination method using the
different time distribution of scintillation light generated in electron recoil
and nuclear recoil interactions. We show that the methodology followed both for
the calibration of the ZEPLIN-I detector response and for the estimation of the
discrimination power is not reliable enough to claim any background
discrimination at the present stage. The ZEPLIN-I sensitivity appears then to
be in the order of 10$^{-3}$ picobarn, three orders of magnitude above the
claimed 1.1 10$^{-6}$ picobarn.
