Cancer therapy is associated with inherent adverse effects and the need for complete, consistent and accurate reporting of toxicity is paramount in multicenter cooperative oncology clinical trials. Accurate toxicity information is essential to weigh the costs and benefits associated with new treatment regimens. A major issue faced by investigators and clinical trial coordinators today is the lack of clear directions regarding what method should be used in toxicity assessment in cooperative oncology clinical trials. Research personnel are faced with two options: (1) to be proactive and use a "directed" method of toxicity assessment or (2) to simply follow the data trail and report selected toxicity based only on routine documentation in the chart. The differences between these two approaches may be immense depending on one's perspective. The purpose of this article is to review how the current methods of toxicity assessment evolved and discuss issues and concerns in toxicity assessment in a challenging healthcare environment where clinical trials continue to increase in complexity and workload through the use of novel and multimodality therapies. The potential implications for toxicity data management practices, data quality, patient care management and resource utilization are discussed.