The excretion of citrulline, a precursor of carcinogenic ethyl carbamate, formed from arginine degradation by malolactic bacteria in wine is of toxicological concern. The arginine metabolism of resting cells of Lactobacillus buchneri CUC-3 and Oenococcus oeni Lo111 was examined. The citrulline excretion rate was found to be linearly correlated to the arginine degradation rate. It was possible to calculate an arginine to citrulline conversion ratio which could be used to predict the amount of citrulline expected after the degradation of a known quantity of arginine. The conversion ratios determined in this study were similar to data calculated from other authors for fermentations in wine and ranged between 4.0% and 7.7%. Ribose, fructose and glucose inhibited the degradation of arginine in Lact. buchneri CUC-3, and inhibition of arginine degradation by glucose correlated with higher arginine to citrulline conversion ratios. The work presents new results of arginine metabolism in malolactic bacteria and gives starting points for investigations in wine.