Nucleotide sequence of a 721 base pair segment of maize chloroplast DNA, encoding the putative chloroplast ribosomal protein S11 at physical map position 33.1-33.5 Kbp, is described. A Shine-Dalgarno sequence and computer-derived stem-loop structures of dyad symmetry are present in the spacer region between rpS11 and its 5' upstream gene rpL36. The deduced amino acid sequence of maize chloroplast S11 shows 69%, 66%, 62%, 57%, 48% and 45% sequence identity to the corresponding sequences of tobacco, spinach, pea, liverwort, Escherichia coli and Bacillus subtilis, respectively, and 41% sequence identity to three eukaryotic cytoplasmic ribosomal proteins, S14 of Chinese hamster and of human and rp59 of yeast. Maize chloroplast r-protein S11 is larger than the other published S11s of plants and bacteria, due to the apparent tandem introduction of a short sequence stretch of internal homology.