  Searches for scalar top and bottom quarks have been performed with data
collected by the ALEPH detector at LEP. The data sample consists of 21.7 pb^-1
taken at sqrt{s} = 161, 170, and 172~GeV and 5.7 pb^-1 taken at sqrt{s} = 130
and 136~GeV. No evidence for scalar top quarks or scalar bottom quarks was
found in the channels stop --> c chi, stop --> b l snu, and sbottom --> b chi.
For the channel stop --> c chi a limit of 67 GeV/c^2 has been set on the scalar
top quark mass, independent of the mixing angle between the supersymmetric
partners of the left and right-handed states of the top quark. This limit
assumes a mass difference between the stop and the chi of at least 10 GeV/c^2.
For the channel stop --> b l snu the mixing-angle independent scalar top limit
is 70 GeV/c^2, assuming a mass difference between the stop and the snu of at
least 10 GeV/c^2. For the channel sbottom --> b chi, a limit of 73 GeV/c^2 has
been set on the mass of the supersymmetric partner of the left-handed state of
the bottom quark. This limit is valid if the mass difference between the
sbottom and the chi is at least 10 GeV/c^2.
