Seeds of most Prosopis species exhibit hard seed coat dormancy which must be broken to permit rapid germination. Pre-treatments tested for breaking the dormancy of Prosopis juliflora seeds consisted of cutting, abrasion, treatment with 30, 60 or 95% sulfuric acid for 2-30 min, boiling water with soaking for up to 5 days, scalding for 2 s to 10 min, and passing through a cow. Sulfuric acid at 95% for 14 or 30 min, 60% sulfuric acid for 30 min, and manual scarification by cutting or abrasion, all gave germination >94%. Immersion in boiling water followed by 24 h soaking, traditionally used by many field workers, gave only 52% germination. Scalding in actively boiling water for 2 s to 1 min gave similar results (55-74% germination). Some 28% of seeds passed through a cow germinated, compared with 13% of untreated control seeds. Abrasion, 95% sulfuric acid for 14 min and boiling water without soaking also increased germination of seeds of P. articulata, P. caldenia, P. cineraria, P. laevigata and P. tamarugo. Scalding for 5 or 10 s increased germination of seeds of each of these species except P. tamarugo in which was reduced by 10 s scalding. With all 6 species, no treatment was more effective than abrasion for breaking the hard seed coat dormancy.