A method and system for detecting and identifying abnormal drilling conditions. It determines the normal pump speed-pressure ratio over the range of usual working conditions. It measures the output pressure from the pump. And it measures the speed of the pump. Then it detects a change from the normal pump speed-pressure ratio which indicates abnormal conditions. Identification of the abnormal condition depends upon whether the pump speed increased above normal or the output pressure decreased below normal. If the former, the volume of drilling fluid returning is observed in order to identify one of three conditions. If the latter, the number of decreases greater than a predetermined extent are counted over a predetermined interval of time which may indicate malfunctioning pump valve or valves.