Abstract: An air or gaseous fluid lubricated penetrometer reduces friction between the soil and the push rod string. Air is pumped into the interior of the string and is directed by exit ports into the annular space between the soil and the outer walls of the string. Without damaging the soil, the air prevents the soil from adhering to the sides of the string and thereby reduces frictional forces that restrict the downward movement thereof. The exit ports in the string are located above the instrument housing so that accurate measurements can be made on the soil properties.