Digestible and metabolisable energy values were determined by the metabolic balance method. The mean (and SEM) metabolisuble energy values for lactitol were 11.8 (0.8) arid 9.8 (1.5) kJ g−1, respectively, for the laboratory rat arid the miniature pig. For lactulose, metabolisable energy values were 8.4 (1.0) and 9.0 (0.8) kJ g‐−1, respectiuely, for the rat and pig. Digestible energy vulues were little different from these metabolisable energy values indicating that the efficiency o f utilisation of the digestion products absorbed may be high. Copyright © 1990 John Wiley & Sons, Ltd