Neurons in the primate dorsolateral prefrontal cortex (dlPFC) filter attended [corrected] targets distinctly from distracters through their response rates. The extent to which this ability correlates with the organism's performance, and the neural processes underlying it, remain unclear. We trained monkeys to attend to a visual target that differed in rank along a color-ordinal scale from that of a distracter. The animals' performance at focusing attention on the target and filtering out the distracter improved as ordinal distance between the stimuli increased. Importantly, dlPFC neurons also improved their filtering performance with increasing ordinal target-distracter distance; they built up their response rate in anticipation of the target-distracter onset, and then units encoding target representations increased their firing rate by similar amounts, whereas units encoding distracter representations gradually suppressed their rates as the interstimulus ordinal distance increased. These results suggest that attentional-filtering performance in primates relies upon dlPFC neurons' ability to suppress distracter representations. Copyright © 2011 Elsevier Inc. All rights reserved.