The purpose of this study was to evaluate the effect of a colutory (XeroLacer, Lacer), prescribed for the treatment of xerostomy, on microleakage into class V cavities filled with a composite (Z100, 3M ESPE) or a compomer (F2000, 3M ESPE) in combination with either a two-step etch-and-rinse adhesive (Adper Scotchbond 1XT, 3M ESPE) or a self-etching adhesive (Adper Prompt L-Pop, 3M ESPE). Class V cavities were made in the buccal surfaces of 80 bovine lower incisors which were randomly divided into four groups (n = 20): (1) Adper Scotchbond 1XT/Z100; (2) Adper Scotchbond 1XT/F2000; (3) Adper Prompt L-Pop/Z100; and (4) Adper PLP/F2000. All specimens were immersed in distilled water for 3 months and ten specimens of each group were immersed and vibrated in XeroLacer for 2 min three times a day. The specimens were dyed with 1% methylene blue for 24 h. Longitudinal sections were made and percentages of microleakage were determined by image analysis. In distilled water, microleakage with the Adper Scotchbond 1XT/F2000 combination was significantly greater than with Adper Scotchbond 1XT/Z100 or Adper Prompt L-Pop/Z100, and microleakage with Adper Prompt L-Pop/F2000 was significantly greater than that with Adper Prompt L-Pop/Z100. No significant differences were detected among the groups exposed to XeroLacer. However microleakage was significantly less with Adper Scotchbond 1XT/F2000 after exposure to XeroLacer than after immersion in distilled water only. In conclusion, exposure to XeroLacer decreased microleakage into cavities restored with the compomer.