Productivity studies are still frequently used to describe, understand and improve forest operations. Delays are recognized as being one of the major factors that limit chipper productivity in most operations and are therefore an integral part of most time studies. Accurately recording and subsequently interpreting delay events is within the relatively short observation period of a typical time and motion study. This paper analyzes the delay component of sixty-three chipper time-study data sets, from thirty-six different chipping machines. All the studies were set up and carried out with the same principal investigator. Three delays' categories were used; mechanical, operator and organizational and other. The overall average utilization of the chipper was 73.8%. Regardless of operation type, two thirds of the total delay time are represented by organizational delays, which emphasizes the crucial role of operation management. Optimization measures should not be limited to the individual machine, but address the operation as a whole. The more productive the operation, the more sensitive it is to both delays as well as poor planning. (C) 2008 Elsevier Ltd. All rights reserved.