Search for top and bottom squarks

Searches for the lightest scalar top quark $\tilde{t}_1$ and scalar bottom quark $\tilde{b}_1$ performed at LEP2 with a center-of-mass energy of up to $\sqrt{s}=209$ GeV and at Tevatron using data collected at $\sqrt{s}=1.8$ TeV during Run I and at $\sqrt{s}=1.96$ TeV during Run II, are discussed. Different possible decay modes were considered and no evidence for any such signal was observed. Exclusion limits were extracted.