Most monitoring ionosonde stations now rely on automatic processing rather than manual processing to provide ionospheric characteristics. A systematic assessment was made of the quality of all the key ionospheric characteristics scaled automatically from hourly ionograms from the midlatitude Chilton ionosonde in the United Kingdom, by comparing them with the definitive values produced by manual scaling. The data for the study were a nearly continuous series of hourly values covering the majority of solar cycle 23 from 1996 to the end of 2004. This period includes solar maximum and minimum conditions and quiet and disturbed intervals, and the investigation is the first comprehensive examination of the performance of automatic scaling without any data preselection over such an extended period. The accuracy of autoscaled values during storm periods was examined against the global storm index Dst for the whole 9-year data set. Geomagnetic conditions were found to have only a small effect on autoscaling performance, with the most important identifiable cause of error being the truncation of automatic layer traces due to broadcast interference. Overall, the performance of the autoscaling algorithms was found to be acceptable, with the characteristics foF2, h′E, M(3000)F2, and MUF(3000)F2 within defined error bounds for more than 90% of the time and all characteristics within these bounds more than 80% of the time.