This in vitro study compared the microleakage of Class 5 amalgam restorations placed in extracted human teeth lined with a 4-META liner (Amalgambond), with similar restorations lined with copal varnish (Copalite). The restored teeth were stored in saline for 1 week, 6 months, and 1 year, then thermocycled, stained with 5% methylene blue, sectioned, and viewed using a light microscope. It was found that at 1 week and 6 months the 4-META group leaked significanlty less than the copal resin group, but after 1 year there was no significant difference between groups.