  A search for stable and long-lived heavy charged particles was performed
using the data taken by the DELPHI experiment at an energy of 189 GeV. The
Cherenkov light detected in the Ring Imaging Cherenkov Detector and the
ionisation loss measured in the Time Projection Chamber were used to identify
heavy particles passing through the detector. No evidence for the production of
such particles has been found, therefore exclusion limits at 95% confidence
level were derived on the masses of left and right handed smuons and staus. The
results were combined with previous DELPHI searches in this channel. Including
previous DELPHI results, masses of left (right) handed stable smuons and staus
can be excluded between 2 GeV/c^2 and 88 (87.5) GeV/c^2 at 95% CL.
