Patients visit the Center 5 times over a 1-year period, usually for 2 to 3 days per visit, for an extensive series of clinical and biochemical tests. Visit 1 is for baseline examinations and blood and urine chemistries and to educate the patient on an LTD. This visit lasts approximately 7 days to determine acceptable circulating tyrosine concentrations for LTD formula at discharge. Patients are provided with tubes to take to local laboratories every 2 weeks for blood work. Patients are readmitted in 1 month to determine adherence to diet and serum tyrosine levels. Patients who evidence dietary compliance, no adverse effects, and a willingness to continue are placed in 1 of 2 treatment arms: DCA plus an LTD plus placebo or DCA plus an LTD plus NTBC. Thereafter, patients return during Months 5, 9, and 13, which completes their 1-year treatment phase.