Four accelerator mass spectrometry (AMS) facilities undertook an interlaboratory exercise designed to examine the reliability and reproducibility of radiocarbon determinations on bone by dating a sample of elk (Alces alces) from Miesenheim IV. This specimen is derived from a secure geological context directly beneath the Laacher See tephra, which provides a precise terminus ante quern of ∼11,060 yr BP (∼13,050 cal yr BP). Regrettably, the results of the intercomparison exercise were complicated by evident contamination of the bone sample by exogenous organic material. This contaminant, probably humic acid, resulted in a wide span of ages (10,010 ± 30 to 11,100 ± 45 BP). The only method that yielded an accurate determination, consistent with the age of the tephra, was Oxford's single amino acid technique, which targets hydroxyproline. An acid hydrolysis step seems to have been crucial in breaking the bonds between the bone collagen and the contaminant.