Rhabdomyosarcoma. From the laboratory to the clinic. The prospect of identifying and developing new agents for treatment of rhabdomyosarcomas is discussed in the light of current prognosis for children with advanced stage disease. Preliminary attempts to identify tumor-specific agents using in vitro cell culture show potential promise, but as yet remain unproven. The more complex system of identifying therapeutically active agents using human tumor xenografts has demonstrated usefulness. The potential problems associated with this system are discussed. 