During recent years, there has been interest in once-a-day (OAD) milking. A comparison was made of OAD with twice-a-day (TAD) milking on a case study farm in northern Victoria. The comparison suggests that operating profit and internal rate of return are similar to TAD milking if the decrease in milk protein plus fat production, as a result of OAD milking, is less than 12 percent. Although a decrease in milk protein plus fat production of this magnitude may be achievable on some farms in Australia, the decrease is likely to be greater than this in many instances, resulting in reduced profit when changing from TAD to OAD milking. To achieve comparable operating profit with OAD milking, a farm system would need to be well suited to OAD milking, and the implementation well planned and executed. The profitability of switching to OAD milking is sensitive to the amount of genuine savings in labour costs or the ability to make real earnings from off-farm employment. For the case study farm analysed, increasing the stocking rate when switching to OAD milking was not an appropriate option when pasture consumption remained the same. On farms where stocking rates are lower or opportunities exist to increase pasture consumption or where cows are consuming less grain per cow and more pasture per cow, it may be profitable to increase stocking rate when switching to OAD milking.