A study to examine the safety (and potential efficacy) of the adult stem cell investigational product, MultiStem, in adults who have Acute Respiratory Distress Syndrome (ARDS). The primary hypothesis is that MultiStem will be safe in ARDS patients.

Inclusion Criteria:

• Diagnosis of moderate to severe ARDS, as defined by the Berlin definition, requiring an endotracheal or tracheal tube
• Able to receive investigational medicinal product within 96 hours of meeting the last of the ARDS diagnosis criterion

Exclusion Criteria:

• Concurrent illness that shortens life expectancy to less than 6 months
• Other serious medical or psychiatric illness