We have developed a rapid and sensitive method to screen the Duchenne muscular dystrophy (DMD) mRNA for translation terminating mutations by a combination of RT-PCR (Reverse Transcription and Polymerase Chain Reaction) and in vitro transcription/translation applied to white blood cell mRNA. This technique was termed the protein truncation test (PTT). Here we demonstrate the detection of a point mutation in a DMD patient and his mother, a carrier. The PTT can also be used for carrier detection when no patient material is available, or in the case of spontaneous mutations. We developed a protocol to screen the total coding region of the DMD gene in 5-10 PTT reactions. Furthermore, PTT could be of diagnostic value in any disease where premature terminations form a substantial part of the total mutation spectrum.