BACKGROUND Although significant progress has been made in the management of children with Wilms tumor, two major controversies still exist: the extent of radiographic evaluation necessary before surgery and the role of preoperative chemotherapy. This study sought to determine whether patients with Wilms tumor who presented with abdominal pain defined a special subset of patients who might require a more extensive preoperative work-up and neoadjuvant chemotherapy. METHODS From 1970 to 1995, 250 children were treated for Wilms tumor at a single pediatric institution. A retrospective chart review determined presenting signs and symptoms for each patient. RESULTS Thirty-four (14%) patients (mean age 5.5 years) sought medical attention with a chief complaint of abdominal pain. The stage distribution for these patients tended to be higher and was significantly different (P <.001, chi(2)-analysis) from those presenting without pain. Four (14%) of 29 patients with tumor available for analysis were found to have anaplastic histology. CONCLUSIONS These data suggest that patients with Wilms tumor who present with abdominal pain represent a special subgroup that tends to be older and has an increased incidence of tumor rupture, anaplasia, and higher stage. These patients may benefit from a more extensive preoperative evaluation and consideration of neoadjuvant chemotherapy.