A comparative study of the (i) extrusion, (ii) melt spinning and (iii) tubular film instabilities of a range of high density, linear low density and low density polyethylene melts is presented. The unique features of the unstable behavior are described for each of these operations. Linear (including linear low density) polyethylenes generally exhibit a slip induced extrusion instability and often several regimes of unstable flow. Long chain branched polyethylenes generally exhibit more stable melt spinning and tubular film characteristics than the linear polyethylenes. Broadening molecular weight distribution of linear polyethylene destabilizes melt spinning behavior, but stabilizes tubular film extrusion. The influence of rheological properties on these instabilities is discussed.