Data from 1357 boars ad libitum fed on a performance testing scheme were analysed to explore the genetic aspects of voluntary food intake. The heritabilities of food intake, daily gain and food/ gain were found to be 0-23, 0-41 and 0-18 respectively. The correlations obtained between gain and intake of 0-63 (phenotypic) and 0-89 (genetic) were typical of those reported for ad libitum feeding but greater than those reported for semi-restricted. Estimates of genetic correlation between gain and efficiency ranged from 0-64 to zero and for the phenotypic correlation from 0-44 to zero and were smaller than those reported for restricted feeding. Correlations between intake and efficiency were highly negative on the phenotypic level but small and of variable size genetically, in contrast to reports of small phenotypic and positive genetic correlations under restriction.