Removing direct current (DC) trends before calculating standard deviations and power spectral densities is a necessary operation, but the choice of method is probably one of the most difficult problems in electrochemical noise measurements. The procedure must be simple and straightforward and must effectively attenuate the low-frequency components without eliminating useful information or creating artifacts. Several procedures are presented, including moving average removal (MAR), linear detrending, polynomial fitting, and analog or digital high-pass filtering. Their effect on electronic and electrochemical signals is discussed. The results show that the best technique appears to be polynomial detrending. In contrast, the recently proposed MAR method was found to have considerable drawbacks and its use is not recommended.