This study will evaluate the effect of single doses of LY3154207 on the amount of time it takes for healthy sleep-deprived men to fall asleep. The study will also estimate how much LY3154207 gets into the blood stream and how long it takes the body to remove it. Information about any side effects that occur will be collected. Each participant will complete four study periods, which will last a total of about 8 weeks.

Inclusion Criteria:

• Overtly healthy males 18 years of age or older who have given consent and are reliable and willing to make themselves available for the duration of the study and are willing to follow study procedures
• Have a regular sleep pattern with routine time spent in bed between 6.5 hours and 9 hours each night

Exclusion Criteria:

• Are shift workers who shifted work within 14 days prior to screening or plan to during the study
• Have a known sleep disorder or history of a sleep disorder
• Have traveled 2 time zones or more within 7 days prior to screening or plan to during the study
• Regularly take naps during the day
• Are hearing impaired