The effects of activated charcoal in the culture medium on regenerant shoots of Arabidopsis thaliana (L.) Heynh. were examined. In these experiments, shoots generated from anther-derived callus were observed to root more frequently on charcoal-containing medium than on medium lacking activated charcoal. Further, concurrent shoot growth and development was greater on charcoal medium than on a rooting medium previously used. Interactions of activated charcoal with exogenously added growth hormones and sucrose as these affected root formation were analyzed in seedling-derived shoots. The action of activated charcoal appeared to be independent of the other factors. Action of charcoal in root promotion probably occurs through adsorption of auxins and/or phenolics originating from the regenerated shoot. The addition of activated charcoal to the rooting was also observed to stimulate flower development and improve floral fertility of A. thaliana. The latter occurrence should improve the usefulness of A. thaliana for somatic cell genetic research.