Distortion of vowels in dysarthria associated with amyotrophic lateral sclerosis can be detected at the perceptual, physiological, and acoustical levels of analysis. Sound spectrography was used to analyse the formants of vowels which reflect position and space of articulatory organs. We analyse status and progression of dysarthria in 54 year old women with amyotrophic lateral sclerosis using sound spectrography. Target formant frequencies were measured from select words containing the vowels /a/, /e/, /i/, /o/, /u/. Results revealed that dysarthric patient exhibited smaller vowel space areas and less systematic changes in vowel spaces for pronouncing different vowels in comparison with normal control. Changes of vowel formants in sound spectrographic analysis reflected progression of dysarthric symptom in this patient. We conclude that acoustic analysis of vowels using sound spectrography is a useful tool to visualize and quantitatively analyse the severity and progression of dysarthria due to paralytic articulatory organ.