The context of the start codon (typically, AUG) and the features of the 5 Untranslated Regions (5 UTRs) are important for understanding translation regulation in eukaryotic mRNAs and for accurate prediction of the coding region in genomic and cDNA sequences. The presence of AUG triplets in 5 UTRs (upstream AUGs) might effect the initiation rate and, in the context of gene prediction, could reduce the accuracy of the identification of the authentic start. To reveal potential connections between the presence of upstream AUGs and other features of 5 UTRs, such as their length and the start codon context, we undertook a systematic analysis of the available eukaryotic 5 UTR sequences.