In this paper we develop a job portfolio model of dual job holding based on a Stone-Geary utility function. We derive the associated Slutsky equation components. Because the job portfolio model applies only to unconstrained dual jobholders, we separate individuals who moonlight because of an hours constraint from dual jobholders who work on two job for reasons different from an hours constraint. Income and wage elasticities are estimated for workers without hours constraints using data from the May 1991 supplement to the Current Population Survey. Our study finds that the income and compensated wage elasticities are much larger for labor supply to job 2 compared with job 1.