Organisms are said to be drug-resistant when drugs meant to neutralise them have reduced effect. When an organism is resistant to more than one drug, it is said to be multi-drug resistant. The most prominent example of this is antibiotic resistance. Drug resistance is also found in some tumour cells, which makes it more difficult to use chemotherapy to attack tumours made of those cells. When a drug such as an antibiotic is administered, those which have a genetic resistance to the drug will survive and reproduce, and the new population will be drug-resistant. This book provides in depth research on multi-drug resistance and its impact on neuorology. This includes studies on GS-X Pump/Multidrug Resistance Proteins, Quantitation of O6 -- Methylguanine, Therapeutic Responses to Chemotherapy, Profiles in Cancer, Neurodegenerative Diseases and Multiple Sclerosis.