A randomized trial of intraeavltary microwave hyperthermia combined with external irradiation (R+II) versus radiation (R) alone in the treatment of esophageal cancer was performed form February 1986 to February 1988. In the R group, radiation was given by 8 MV Xray with 2 Gy/fraction, 5 fractions per week with a total dose of 60 Gy/6 weeks. In the R+H group, the radiation was given as R group but with a total dose of 40 Gy/4 weeks, lntracavitary 915 Mhz microwave hyperthermia was given with a nominal temperature of 43.5°C at the margin of the tumor surface, 45 minutes/session, 1-2 sessions/week for 4-8 session. The 1-, 3-, and 5-year survival rates in R+H group were 81.2% (48/59 cases), 42.4% (25/59) and 23.7% (14/59), while in the R group 59.0% (39/66 cases), 24.2% (16/66) and 16.7% (11/66) respectively. The differences in 1- and 3-year survival rates were statistically significant (P<0.05) between the 2 groups. Using the thermal dose T90 analysis, after the cases with T90<43°C (insufficient thermal dose) were eliminated, 52 cases with T90 equal to or higher than 43°C had 1, 3, and 5 year survival rates of 84.6%, 44.2% and 26.9%, respectively. Statistically significant differences in the 2 groups were also limited only to 1- and 3-year survivals, ttigher 5-year survivals is anticipated if more cases are studied.