Combination therapy with GLV-1h153 and 131I mediates enhanced tumor kill. Although groups of mice treated with PBS, GLV-1h153 alone, and 131I alone continued to experience rapid tumor growth in radiovirotherapeutic experiment, mice treated with GLV-1h153 plus 131I experienced retardation and even regression of tumor volume. Statistical analysis was performed using 1-way ANOVA. **P, 0.01 for comparison of untreated control, GLV-1h153, or 131I groups alone with GLV-1h153 plus 131I groups. *P, 0.05 for comparison of untreated control, GLV-1h153, or 131I groups alone with GLV-1h153 plus 131I groups.