Let {X i , i ≥ 1} be a sequence of random variables. This paper studies when the following self-centred, self-normalized central limit theorem holds:where X = n+1 i=1 X i /(n + 1), → L stands for convergence in distribution and N(0, 1) for a standard normal distribution. It is shown that if (1) X i 's are independent identically distributed with X 1 in the domain of attraction of the normal law (DAN), (2) X i 's are exchangeable with mixands in the DAN in probability, or (3) X i 's are stationary with EX 2 1 < ∞, uncorrelated, uniform mixing with appropriate mixing coefficients, then ( * ) holds. Since the results depend on variables that can all be calculated explicitly from the data, they provide a powerful method for statistical testing. An application from the stock market is briefly discussed.