Apparatus for transcutaneous electrical nerve stimulation in humans, comprising a housing; stimulation means mounted within the housing for electrically stimulating nerves; an electrode array releasably mounted to the housing, connectable to the stimulation means, and comprising electrodes for electrical stimulation of nerves; control means mounted to the housing and electrically connected to the stimulation means for controlling the stimulation means; monitoring means mounted to the housing and electrically connected to the stimulation means for monitoring the stimulation means; user interface means mounted to the housing and electrically connected to the control means for controlling the stimulation means; display means mounted to the housing and electrically connected to the control means and the monitoring means for displaying the status of the stimulations means; and a strap attached to the housing and configured to hold the housing, stimulation means and electrode array at a specific anatomical location to treat pain.