The volume of some tumors correlates with local disease control, response, and survival. Small cell lung carcinoma presents with variable and often large intrathoracic masses. We assessed volume by two methods (summation of cross-sectional areas and Simpson's rule for estimating volume) and correlated volume with treatment outcome. Twenty-nine patients with small cell lung carcinoma (12 limited disease and 17 extensive disease) were analyzed for volume outcome correlations. There were five early deaths. Twenty-four had response correlations (11 limited disease and 13 extensive disease). Eighteen of the twenty-four achieved complete response. There was no apparent correlation between complete and/or partial response and pretreatment tumor volume. There was no apparent correlation between survival and volume. The methods of volume assessment correlate well with each other (r = 0.88) and either can be used with accuracy. So far there is also no correlation between chest tumor volume and intrathoracic recurrence. Our projections suggest that there is a low probability of correlating chest tumor volume and either response or survival. This is in keeping with the disseminated nature of the tumor which is its limiting factor in survival.