The stability of plants growing on a slope may be affected by factors that tend to uproot the plant. To avoid uprooting, roots undergo complex, finely regulated changes. Spanish broom (Spartium junceum L.) is a widespread Mediterranean legume that frequently grows on slopes. Using twodimensional polyacrylamide gel electrophoresis (2D-PAGE) we compared the protein patterns of S. junceum roots grown in a greenhouse in either upright or tilted pots. We obtained about 1000 protein spots that were highly reproducible across an isoelectric focusing range 4–7. The protein profile of 141 spots differed significantly ( p < 0.001) between the two conditions. Based on spot quantity and quality, and the expression rate in the two conditions, 34 protein spots (20 up-regulated and 14 down-regulated in the slope condition) were selected for tandem mass spectrometry analysis. The peptide sequences were obtained by querying the sequences of two databases: an EST database containing DNA sequences of approximately 550,000 ESTs of seven species of the Fabaceae family and the SwissProt database. The function of 18 proteins was assigned by homology; the remaining proteins did not show any alignment with the sequences of the two databases. Most of the proteins whose expression differed between the two conditions showed homology with proteins involved in cell structure organisation and in several stress responses of diverse plant species. The data from this investigation are available at http://cbi.labri.fr/outils/protic/ProticDB.php.