A search in the H1 experiment at HERA for scalar and vector leptoquark
s, leptogluons and squarks coupling to first generation fermions is pr
esented in a data sample corresponding to an integrated luminosity of
425 nb(-1). For masses ranging up to similar to 275 GeV, no significan
t evidence for the direct production of such particles is found in var
ious possible decay channels. At high masses and beyond the centre of
mass energy of 296 GeV a contact interaction analysis is used to furth
er constrain the couplings and masses of new vector leptoquarks and to
set lower limits on compositeness scales.