Residential septic tank-seepage pit systems designed to FHA standards performed satisfactorily in the Anchorage and Fairbanks, Alaska, areas. Fifty percent of 127 systems observed in Anchorage functioned 10 years without malfunction; in Fairbanks 50 percent of 46 systems observed functioned 6.5 yr without malfunction. Most malfunctions were due to failure of the secondary absorption systems. A substantial number of cases of early failure were observed in both areas caused by defects in design or construction. Temperature measurements made on 20 septic tanks and seepage pits showed that septic tank contents remained above 48° F (8.9° C) during the winter and that freezing in the secondary systems was not a problem. Adequate treatment was obtained at this temperature.