In the spring of 2000, a cluster of indistinguishable Shiga toxin-producing Escherichia coli (STEC) O26:H11 was identified in Germany by molecular subtyping surveillance. An investigation was prompted to identify a common source of exposure. A case subject was defined as a person having a polymerase chain reaction-confirmed STEC O26 infection between March and April 2000, irrespective of clinical signs, and whose isolate was indistinguishable from the index strain by use of pulsed-field gel electrophoresis. Eleven case subjects were found in 5 institutions that were supplied by 4 kitchens located in 3 states. The median age was 2 years (range, 2-31 years). No bloody diarrhea was reported, and 5 persons remained asymptomatic. Comparison of invoices revealed a certain type of beef ("Seemerrolle") as possible source of infection. This is, to our knowledge, the first multistate outbreak associated with a non-O157 STEC detected by laboratory-based surveillance. Molecular subtyping was pivotal, as disease occurrence was sporadic or family-related.