This multiple-center, multiple-dose, randomized, double-blind, double-dummy, placebo-controlled, positive-controlled, parallel group study will investigate the effect of RO4917838 on the QTc interval in healthy volunteers. Healthy volunteers will be randomized to one of 4 treatment arms; Arm A: low dose of RO4917838, Arm B: high dose of RO4917838, Arm C: placebo to RO4917838 and moxifloxacin on Day 1, Arm D: placebo to RO4917838 and moxifloxacin on Day 11. The anticipated time on study treatment is 11 days.

Inclusion Criteria:

• Healthy male volunteers aged 18 to 65 years inclusive
• Body mass index (BMI) between 18 and 30 kg/m2 inclusive.
• Have no contraindications from the following: a detailed medical and surgical history, and a complete physical examination
• Able to participate, and willing to give written informed consent and to comply with the study restrictions

Exclusion Criteria:

• History of any clinically significant gastrointestinal, renal, hepatic, broncho-pulmonary, neurological, mental, cardiac, vascular, endocrinological, hematological or allergic disease, metabolic disorder, cancer or cirrhosis.
• History of alcohol and/or drug abuse or addiction within the last 2 years prior to Day 1 of the study.
• Consumption of nicotine and/or tobacco containing products within the last 3 months prior to Day 1 of the study.
• Infection with human immunodeficiency virus, hepatitis B and/or hepatitis C
• Any condition or disease detected during the medical interview / physical examination that would render the subject unsuitable for the study, place the subject at undue risk or interfere with the ability of the subject to complete the study in the opinion of the Investigator.
• Positive drug screen or alcohol test at screening or prior to enrollment.
• Coffee or tea consumption > 10 cups per day or methylxanthine containing drinks >1.5 liter/day or more than 250 g/day of chocolate.
• Alcohol consumption averaging > 3 drinks daily