The issue of take-up of means-tested benefits is of long standing concern in social policy debates. This paper analyses take-up of Family Income Supplement (FIS) using the Australian Bureau of Statistics' 1986 Income Distribution Survey (IDS). Although FIS was replaced by the Family Allowance Supplement in 1987, the IDS is the most recently available data source that can be used to estimate take-up levels and identify possible factors that may explain take-up of similar benefits. This paper estimates take-up by comparing the number and characteristics of persons who said they were currently receiving FIS at the time of the survey with the number whose current income and family characteristics appeared to make them eligible for FIS. Although estimates of take-up are quite low and raise a number of concerns about the effectiveness of income-tested supplements in reaching the groups they are intended to assist, the main conclusion of the paper is that results using IDS data should only be regarded as approximations. It is suggested that an appropriate approach to understanding and analysing take-up of FAS in the future may involve a survey specially designed to monitor take-up.