Fermilab-Tevatron collider. Measurement of J/PSI production in pbar p collisions at centre-of-mass energy 1.8 TeV. Estimates are given of the b-quark cross section and the fraction by J/PSIs produced from b-quarks. Data come from 1992-1993 collider run and represent a total integrated luminosity of 6.6 pb-1.. Numerical values suuplied by C. Murphy.