Our hypothesis was that a low concentration (30%) of phenol would be more effective than a high concentration (80%) in the treatment of pilonidal disease. The purpose of our study was to compare the effects of high and low doses of liquid phenol in the treatment of pilonidal disease, since the phenolization technique and concentration of the phenol solution is not well defined. Consecutive patients being treated for pilonidal disease with high and low concentrations of phenol were included in this randomized prospective study. The demographic data, pilonidal disease characteristics, and results of phenol application were examined. Of 101 subjects, 52 were treated with 80% phenol while 49 were treated with 30% phenol. The mean observation period was approximately 1 year. The total recovery rate was higher among the 80% phenol group (P = 0.046). The recovery period, the period of leave from work, and complication rates were similar in both groups (P = 0.414, 0.328, 0.256). Also, in the Likert-type survey administered by validated methods, there was no difference in the degree of satisfaction (P = 0.494). The low concentrations of phenol did not achieve faster recovery, faster return to work, or fewer complications in the treatment of pilonidal disease. An 80% concentration of phenol should be used for a higher rate of recovery.