The polyethylene caulking composition of the invention is a mixture of a carrier and binder component and polyethylene powder. The carrier and binder component is a liquid hydrocarbon oil. The polymer is finely subdivided polyethylene, preferably ultra high molecular weight, having a low melt index, no greater than 30. The composition is thixotropic with a consistency of toothpaste, typically having a stirred viscosity up to 30,000 centipoise at ambient temperature, which is suitable for use as a caulking composition.The caulking composition of the invention can be extruded at low pressures through a caulking gun or from a squeeze tube to plug vent holes or perforations in molded, hollow-form polyethylene parts, or applied as a caulk onto the flange surfaces of rotational molds.