Competition among hospitals and managed care have forced hospital industry to be more efficient. With higher degrees of hospital competition and managed care penetration, hospitals have argued that the rate of increase in hospital cost is greater than the rate of increase in hospital revenue. By developing a payer-specific case mix index (CMI) for third-party patients, this paper examined the effect of hospital case mix on hospital cost and revenue for third-party patients in California using the hospital financial and utilization data covering 1986-1998. This study found that the coefficients for CMIs in the third-party hospital revenue model were greater than those in the hospital cost model until 1995. Since 1995, however, the coefficients for CMIs in the third-party hospital revenue model have been less than those in hospital cost models. Over time, the differences in coefficients for CMIs in hospital revenue and cost models for third-party patients have become smaller and smaller although those differences are statistically insignificant.