The case of a spherical vapor bubble growing in an infinite, uniformly heated liquid, has been analyzed under the thin boundary layer approximation for the effects of a variable pressure field, including density variation. It has been shown that, in addition to the usually accepted effects of initial superheat, variable pressure effects can be quite important and dominate the rate of growth. For the case where pressure changes cause the vapor temperature to behave as tn , (t being time), the bubble radius will grow as tn+1/2 , significantly faster than the t behavior usually expected. The analysis has been shown to compare favorably with existing data.