This randomized, double-blind, placebo-controlled study will assess the safety, tolerability and pharmacokinetics of RO5024048. Japanese and Caucasian healthy volunteers will be randomized to receive either single oral doses of RO5024048 or placebo. Follow-up is 7-10 days.

Inclusion Criteria:

• Healthy male and female adults, 20 to 55 years of age, inclusive
• Body mass index (BMI) 18 - 30 kg/m2 inclusive
• Non-smoker, or previous smoker who discontinued smoking >/= 6 month prior to study entry
• Japanese subjects must be first generation: born in Japan, not having lived outside Japan >5 years, able to trace maternal and paternal Japanese ancestry
• Female subjects of childbearing potential and male subjects and their partners of childbearing potential must agree to use two forms of contraception
• Agree to abstain from alcohol consumption and from strenuous exercise up to 3 days before dosing and throughout study (including the follow-up visit)

Exclusion Criteria:

• Positive pregnancy test
• Males whose female partner is pregnant or trying to become pregnant
• Positive urine test for drugs of abuse
• Positive for alcohol
• Positive result on hepatitis B, hepatitis C, or HIV test
• Clinically significant disease or abnormalities in laboratory parameters
• Participation in an investigational drug, biologic or device study within 3 months before study drug administration
• Donation or loss of any blood over 450 mL within 3 months before study drug administration