The Arabidopsis thaliana Em1 gene has been mapped to the lower arm of chromosome III. Fine analysis of 60 kb around this gene, based largely on identification and sequencing of cognate cDNAs, has allowed us to identify 15 genes or putative genes. Cognate cDNAs exist for ten of these genes, indicating that they are effectively expressed. Analysis by sequence alignment and intracellular localization prediction programs allows attribution of a potential protein product to these genes which show no obvious functional relationship. Comparison of the true exon/intron structure based on cDNA sequences with that proposed by three commonly used prediction programs shows that, in the absence of further information, the results of these predictions on anonymous genomic sequences should be interpreted with caution. Examination of the non-coding sequence showed the presence of a novel repeated, palindromic element. The results of this detailed analysis show that in-depth studies will be necessary to exploit correctly the complete A. thaliana genome sequence.