D. Research Design and Methods Ten patients will be recruited to participate, and will have serial muscle ultrasound examinations every three months, at regularly scheduled clinic appointments in the Vanderbilt ALS clinic. Muscles examined will include forearm flexors, biceps, and tibialis anterior. The thickness of each muscle will be measured at standard sites for these muscles, in addition to the echogenicity as measured by a grayscale histogram representation. The rate of loss of ultrasound-measured muscle thickness will be assessed over time. Our hypothesis is that there will be significant loss of muscle thickness over time, which will correlate with disease severity. As different patients have different rates of deterioration, there will likely be significant differences in the rate of muscle volume loss from patient to patient. A secondary endpoint will be an increase over time in muscle echogenicity. Patients will complete the ALS Functional Rating Scale (ALSFRS-R), a 12 item subjective scale that assesses several motor functions, including function of speech, swallowing, respiration, and activities of daily living. Grip strength will be measured by hand grip dynamometry, using the best result from 3 attempts in each limb. Secondary analyses will also be conducted to correlate the decrease in ultrasound-measure muscle depth with the ALS Functional-Rating Scale, and with measures from hand grip dynamometry.