We report laser‐induced breakdown studies of laboratory air using 0.266, 0.355, 0.532, and 1.06 &mgr;m radiation for focal spot varying from 30 to 100 &mgr;m. The breakdown intensities were measured for two pulse widths for all four wavelengths. We observe at−0.5pdependence of pulse width on threshold field at 0.532, 0.355, and 0.266 &mgr;m while for 1.06 &mgr;m the pulse width dependence oft−0.35pis observed.