Amyotrophic lateral sclerosis (ALS) related disorders are considered to be uncommon. We hypothesize that urinary dysfunction may occur in ALS patients in the context of spasticity of pelvic floor musculature. We recorded data on 54 subjects with ALS. All subjects were evaluated with ALSFRS and M-Ashworth Scale for lower limbs. Bladder scan procedure was performed to asses post void residual (PVR) in all subjects. Forty-one percent of subjects were symptomatic for urinary disorders and 35% of subjects had a PVR > 50 ml. Linear correlation was found between PVR and ALSFRS with a R(2) 0.95 and p = 0.025; a linear correlation was also noted between PVR and lower limbs Ashworth Scale. We conclude that urinary retention is common in ALS. Urological evaluation is indicated in ALS patients with prominent spasticity.