This publication presents estimates of apprentice and trainee activity in Australia for the December quarter 2011. The figures in this publication are derived from the National Apprentice and Trainee Collection no.71 (March 2012 estimates). The most recent figures in this publication are estimated (those for training activity from the June quarter 2010 to the December quarter 2011). Estimates take into account reporting lags that occur at the time of data collection. Consequently, the figures in this publication may differ from those published in earlier or later reports. Estimated data are presented in this publication on a seasonally adjusted, quarterly and 12-month ending series basis. The 12-month ending series is particularly useful in showing longer-term data trends, but is less useful in identifying turning points. The seasonally adjusted data involve the use of a mathematical model to smooth out fluctuations due to seasonal influences. Seasonally adjusted data are useful to illustrate trends from one quarter to the next, but cannot be further disaggregated. There were 449,000 apprentices and trainees in-training as at 31 December 2011, an increase of 2.5% from the previous year. In the 12 months to 31 December 2011, compared with the previous year: (1) commencements increased by 1.4%, to 318 400; (2) completions increased by 6.9%, to 180 000; and (3) cancellations and withdrawals increased by 5.6%, to 138 600. For seasonally adjusted data, comparing the December quarter 2011 with the September quarter 2011: (1) commencements in trades occupations decreased by 1.3%; (2) commencements in non-trades occupations increased by 1.3%; (3) completions increased by 1.3%; (4) cancellations and withdrawals decreased by 1.1%; and (5) in-training numbers increased slightly. (Contains 19 tables, 3 figures and 5 notes.) [Funding for this paper was provided through the Department of Industry, Innovation, Science, Research and Tertiary Education.]