  Data from HERA, LEP and the Tevatron, as well as from low energy experiments
are used to constrain the scale of possible electron-quark contact
interactions. Different models are considered, including the most general one,
in which all new couplings can vary independently. Limits on couplings and mass
scales are extracted and upper limits on possible effects to be observed in
future HERA, LEP and Tevatron running are estimated. Total hadronic
cross-section at LEP and e-p scattering cross-section at HERA are strongly
constrained by existing data, whereas large cross-section deviations are still
possible for Drell-Yan lepton pair production at the Tevatron.
