In the European Union, the pediatric medicines regulation in 2007 modified significantly the access to new agents in pediatric oncology. Early oncology trials are still thought to be associated with limited benefit and substantial risk. We report the characteristics and outcome of patients below 21 years enrolled in investigational trials in the Pediatric and Adolescent Department at Gustave Roussy between January 2000 and December 2012. A total of 235 patients (median age, 10.4 [0.8 to 20.7] y) were included in 26 trials (16 cytotoxic and 10 targeted agents) for a total of 260 inclusions. A total of 117 patients (50%) had brain tumors and 68 (29%) had various soft tissue and bone sarcoma. Thirteen of the 106 patients in a phase I trial experienced dose-limiting toxicity. Main severe toxicity was hematologic; none had toxic death. Grade 3 to 4 toxicities were associated with combination trials, cytotoxic agent, and at least 1 previous line of therapy. Thirty patients (12%) had objective response and 42 (16%) had stable disease for >4 months. Median overall survival was 9.0 months (95% CI, 7.5-10.5) and 73% of patients received further anticancer treatment. Phase I to II pediatric oncology trials are safe, associated with clinical benefit, and can be successfully integrated in current relapse strategies.