The aim of the study was to assess dysarthria in ALS subjects using acoustic speech analysis. The study was performed in 47 definite or probable ALS patients aged 29-76 years (mean age 53.7 yr.) and in 30 age and sex matched healthy control subjects. Neurological examination showed 15 dysarthric ALS subjects. Acoustic speech analysis is a quantitative, computer-acoustic method estimating dysarthria and based on assessing of sound distance from speech sound tests. In both group the mean sound distance between chosen sounds was compared to a basic pattern and was measured on time-frequency computer acoustic analyses (delta f = 125 Hz, delta T = 9 ms, delta s = 0.5 dB). Our results demonstrated that all sounds were incorrect in all ALS subjects. These abnormalities were significantly increased in the dysarthric ALS subjects. The mean sound distances which separated ALS from control subjects is 0.2 (by Euclidian principle) in 4 out of 5 measured sounds. We suggest that it is possible to detect and measure dysarthria in ALS patients based on the acoustic speech analysis, also in the limb onset ALS subjects.