Expression of CD44 was examined by immunohistochemistry in 205 primary neuroblastomas together with histological grading according to the Shimada classification at the time of diagnosis. In addition, Southern blot analysis to determine N-myc gene amplification was carried out in the same tissue. When compared with clinical data such as stage, age and event-free survival probability it was found that CD44 expression characterizes well differentiated tumours and thus correlates with prognosis (event-free survival probability in CD44 positive patients 0.6 (n = 129) vs. 0.0 (n = 21) in CD44 negative patients). In tumours with N-myc = 1, CD44 positivity was found in 91% of patients as compared to 57% of patients with N-myc > 1 in tumours. All tumours of 13 patients with metastatic stage 4s (with good prognosis) showed CD44s expression. Thus, detection of CD44s expression might serve as a prognostic indicator which can be rapidly detected at diagnosis.