Sulfolobus solfataricus used 2-propanol and 2-propanone ( acetone) when grown in static cultures at 78degreesC with or without glucose at 10 g l(-1). The presence of 3.92 g 2-propanol l(-1) in both cases inhibited growth. However, acetone accumulation following 2-propanol depletion suggested that 2-propanol was co-metabolized via the acetone metabolic pathway. Glucose at 10 g l(-1) increased 2-propanol and acetone utilization from 0.93 g l(-1) to 1.77 g l(-1) and from 0.11 g l(-1) to 1.62 g l(-1), respectively. Without glucose, immobilized S. solfataricus cells increased the 2-propanol removal rate to 0.035 g l(-1) h(-1), compared to 0.0012 g l(-1) h(-1) by its suspended counterpart. The results suggest the establishment of an immobilized reactor configuration is preferential for the treatment of high temperature solvent waste streams by this acidothermophilic Crenarchaeon.