The soybean leghemoglobin lba gene promoter sequence was determined and aligned with the promoter sequence of the soybean lbc3 gene from the same gene family. Five highly conserved regions were found. There are two large conserved regions, one of which overlaps the basic promoter while the other defines a minimal enhancer in the upstream positive elements. Within the minimal enhancer, an inverted repeat with similarity to the binding site of a yeast transcription factor, GCN4, was found. This particular repeat is conserved in the promoters of all functional soybean lb genes as well as in lb gene promoters from other legumes. This suggests that the inverted repeat is important for leghemoglobin gene expression.