The percent of marrow blasts on day 7 of therapy was determined for 128 children with previously untreated acute lymphoblastic leukemia and white blood count (WBC) ± 50,000/μl and/or lymphomatous features enrolled in the Childrens Cancer Study Group trial of the Berlin Frankfurt Munster 76/79 regimen (CCG‐193P). Patients received four‐drug induction therapy including vincristine, prednisone, l‐asparaginase, and daunomycin. Ninety‐seven patients had fewer than 25% marrow blasts on day 7. Of these, 94 survived and maintained remission through day 28 and were designated early responders. Thirty‐one patients had greater than 25% marrow blasts on day 7. Of these, 28 survived and achieved remission on day 28 and were designated late responders. The outcome of patients who underwent a day 7 marrow aspiration was similar to those who did not. Early responders had a 77.4% ± 4.5% (standard deviation) 3‐year estimated disease free survival, while late responders had 47.3% ± 9.8% (P<0.001). Early responders had a superior outcome both in the subset with an initial WBC<50,000/μl (P = 0.025) and in the subset with a WBC ± 50,000/μl (P = 0.01). The day 7 marrow response had prognostic value in this population of children with unfavorable presenting features who received four‐drug remission induction therapy. Copyright © 1990 Wiley‐Liss, Inc., A Wiley Company