Background: The prognosis of adult RMS has been considered dismal. The question is raised that VAC chemotherapy may not be administered as per schedule for adult RMS, consequently low DI leads to poor prognosis. Herein, we examined whether the administration of VAC chemotherapy for adult RMS is feasible with regard to the DIs of V and C. Methods: We extracted the data on adult RMS from pts aged greater than or equal to 21 years. Chart review was performed for all identified pts. DI for V or C was calculated according to the following formula: DI (V) = Total dose of V (mg/m²)/[(last date of injection – first date of injection) + 7]/7 or DI (C) = Total dose of C (mg/m²)/[(last date of injection – first date of injection) + 21]/7, respectively. The percentage of relative DI (RDI) was calculated according to the Children's Oncology Group D9803 protocol. Further, we examined the DI in the first 6 cycles of VAC (induction phase) and the DI after the first 6 cycles of VAC (maintenance phase). Results: We identified a total of 27 pts, and a total of 316 cycles of VAC were administered. In the induction phase, the median DIs (mg·m^-2·week^-1) of V and C were 1.09 and 684.4, respectively. The RDIs for V and C were 81.3% and 93.3%, respectively. In the maintenance phase, the DIs of V and C were 0.77 and 508.0, respectively, while in the maintenance phase, the RDIs for V and C were 51.1% and 69.2%, respectively. The number of pts with RDI more than 80% in the induction phase significantly decreased in the maintenance phase for V (p = 0.0008). Lower RDI of C in the maintenance phase was also showed borderline significance (p = 0.09). In the induction phase (total 168 cycles), the following adverse events were observed: grade 4 neutropenia (77.4%), grade 3/4 anemia (45.8%), grade 4 thrombocytopenia (14.9%), grade 3/4 febrile neutropenia (38.1%), and grade 2 peripheral neuropathy (40.7%). Conclusions: The RDIs of V and C in the maintenance phase were significantly lesser than the corresponding values in the induction phase. Low RDI was mainly attributable to hematologic toxicity and peripheral neuropathy. The maintenance phase chemotherapy for adult RMS should be developed urgently.