In the financial year 1980/81, the public sector borrowing requirement reached the estimated record level of £13.5 billion. This was despite the best efforts of a Government committed to reducing public expenditure. But ten years ago, few people had heard of such a requirement. What in fact is the PSBR, as it is clumsily known? Why is it proving so difficult to control? How does it relate to interest rates and the money supply? Economists and politicians, as usual, cannot agree. What follows, though, should be a help in keeping up with the arguments.