Counts of aerobic mesophilic micro-organisms and aerobic mesophilic spore-forming bacteria were determined in 91 ultra-high-temperature (UHT) commercial Brazilian samples. Forty-six sporeforming bacteria were identified and characterised in terms of their spoilage potential. Among the 20 brands evaluated, 45% had counts of aerobic mesophilic micro-organisms higher than 1.0 9 102 cfu/mL. The sporulated bacteria were identified as Bacillus subtilis/amyloliquefaciens, Bacillus licheniformis, Bacillus pumilus and Bacillus megaterium, and 31% and 33% showed proteolytic and lipolytic activity, respectively. Our findings indicate that there is a potential risk of UHT milk samples becoming spoiled during their commercial shelf life.