Experiments were conducted from 1985 to 1989 to evaluate the response of radishes (Raphanus sativus L.) to N fertilization on Histosols. Three of these experiments used 15N-labeled fertilizer to evaluate the recovery of N by radishes. There was no response to N fertilization in seven of the eight experiments, even though some of them were conducted under conditions of high rainfall. The one experiment in which radish yields increased with N was conducted in a poorly drained, waterlogged field that was atypical of normal radish production fields. Recoveries of fertilizer N in the marketable radish roots averaged 19%. The results of N and 15N analysis showed that although fertilizer N was available for uptake, so was an ample amount of soil mineralized N. These results indicate that under typical growing conditions, radishes produced on Florida Histosols do not respond to N fertilization.