A variety of soil-dwelling microorganisms play a role in the decomposition of interred human skeletal remains, leading to post-mortem alterations in biochemical composition and microstructural appearance of bone. Piepenbrink (1986) has suggested that a post-mortem microbial invasion may be responsible for the fluorescence found in Sudanese Nubian skeletons (AD 350-550) and that the <i>in vivo</i> incorporation of tetracycline, posited by Bassett et al. (1980) to be the causal mechanism, is a misinterpretation of the evidence. While we recognize the potential for post-mortem diagenesis, chemical and histological analyses of the exceptionally well-preserved Sudanese Nubian skeletons confirm our original hypothesis of an <i>in vivo</i> mode of incorporation of tetracycline with subsequent deposition of a permanent, discrete fluorescent label in the bone. Ingestion of tetracycline, a broad spectrum antibiotic, may explain the low rate of infectious disease documented in this population in an earlier study (Armelagos, 1968, 1969). Consequently, it is important that evidence should not be dismissed as merely the result of taphonomic process, without proper consideration of alternative explanations. This note addresses the disparity between the pattern of fluorescent labelling present in Piepenbrink's sample(s) due to diagenesis and the <i>in vivo</i> incorporation of tetracyclines found in the Sudanese Nubian population. -- AATA