An observational field study gives an account of error types, error handling time and use of support in case of an error situation when working with computers in the office. Subjects were 198 clerical employees from 11 companies and seven small firms in Germany. The analyses are based on 1155 observed errors which were concordantly classified into an error taxonomy by two independent re‐raters. Clerical employees spent approximately 10 per cent of their computer working time handling errors. Error handling time is also positively related to indicators of emotional strain. Although the tasks performed were largely routine, more than 11 per cent of all errors required the use of supports such as advisory services, co‐workers, on‐line help and menus or user manuals. Different error classes showed variations in the amount of support used and in error handling time. On the basis of the results, we discuss how the error taxonomy and measures of the human error handling process can be of practical use for evaluation in software ergonomics and for improving human error handling while interacting with computers. 1993 The British Psychological Society