Inclusion Criteria:

- clinically probable-laboratory supported, clinically probable, or clinically definite
amyotrophic lateral sclerosis

Exclusion Criteria:

- Allergic or idiosyncratic response to tamoxifen.

- Other active neurologic diseases that may produce weakness, sensory loss, or
autonomic symptoms.

- Psychiatric, psychological, or behavioral symptoms that would interfere with the
subject's ability to participate in the trial.

- Clinically significant cardiac, pulmonary, gastrointestinal, hematologic, or
endocrine (poorly controlled insulin-dependent diabetes mellitus or hyperthyroidism)
disease that may confound interpretation of the study results.

- Previous kidney or pancreas transplants.

- Significant hepatic or renal disease (AST > 5 times normal, serum creatinine > 2.0
mg/dL for males or > 1.8 mg/dL for females).