Retreatment of previously lased areas of port wine stains can offer significant additional improvement over initial results. From 1977 to 1981 123 patients were subjected to 191 treatments employing the argon laser using an individually varied minimal power dose. Thirty-three areas have been treated a second time a year after the first therapy and six doubly treated areas have also been studied. The additional improvement achieved by retreatment together with the minimal additional chance of complication adds to the safety and practicality of minimal dosage technique. The theoretical considerations allowing successful retreatment are presented and the results of this approach are demonstrated. The timing of retreatment and its limitations are also considered.