The aim of this study is to survey the effect of Tamoxifen in motor neuron disease (MND) patients, amyotrophic lateral sclerosis (ALS) with regular riluzole usage. TDP-43 is related to ALS. Increased the ubiquitinated or phosphorylated TDP-43 can cause animal model of ALS, and TDP43 can be degraded either by proteasome or autophagy pathway system. Autophagy pathway can be activated by mTOR inhibition, resulting in ameliorating TDP-43 accumulation and rescue in motor function in animal model. Tamoxifen had shown ability of enhance both proteasome and autophagy pathway, therefore the investigators assume that Tamoxifen probably can ameliorate TDP-43 accumulation and inclusion body formation in ALS.

The investigators will assess the ALSFR-s in ALS patients at start, 1, 3, 6 and 12 months and correlate the score to the neurological outcome of the patients with and without tamoxifen treatment at dose of 40mg daily for one year.

The study will be able to prove the investigators hypothesis: Tamoxifen, a protease and autophagy enhancer, has synergic effect with riluzole in ALS patients to slowing the progression of neurological dysfunction, and respiratory insufficiency.

Inclusion Criteria:

1. Clinical diagnosed and confirmed ALS patients, with regular follow up and oral form riluzole at National Taiwan University or Shuang- Ho Hospital for more than 6 months.
2. Age ≧20 years old

Exclusion Criteria:

1. Patients who had already ventilator dependent, not regular followed up for more than 6 months or against medical advice, refuse to follow up at neurology department will be excluded in this study.
2. Patients with now or previous usage of Tamoxifen
3. Patients with any contraindications of Tamoxifen usage
4. Patients with other internal medicine illiness