(maximum tolerated dose) The highest dose of an agent that an organism can be exposed to without causing death or significant overt toxicity. Found on http://experttoxicologist.com/tcas-glossary.aspx
The highest dose of a drug or treatment that does not cause unacceptable side effects. The MTD is determined in clinical trials by testing increasing doses on different groups of people until the highest dose with acceptable side effects is found. Also called maximum tolerated dose. Found on http://www.cancer.gov/dictionary?expand=M