In a retrospective study we analzyed the expression of metallothionein (MT) in initial acute lymphoblastic leukemia (ALL) of 92 children and in relapsed ALL of 27 children using immunohistochemistry. MT expression was detectable in 33% of the patients with initial ALL and in 33% of the patients with relapsed ALL. No differences were seen concerning the intensity and the proportion of positively stained cells between initial and relapsed patients. The expression of MT was independent of clinical prognostic factors such as age, sex, immunological subtype, and initial blast cell count. Patients with initial ALL and MT expression tended to have a lower probability of disease-free survival compared with the MT-negative group. The relapsed patients with MT expression showed also a trend toward a shorter survival in comparison to the MT-negative group. However, the differences were not statistically significant. Thus, the results show that MT expression is not an important prognostic factor in the clinical drug resistance of childhood All.