Gregory House lives in apartment 221B during House M.D. The address is a deliberate reference to 221B Baker Street, the London home traditionally associated with Sherlock Holmes.
House's connection to Holmes extends beyond the apartment number. Both characters are exceptionally observant investigators who use deduction to solve difficult problems, and both can be dismissive of ordinary social conventions. House's friend James Wilson occupies a role that parallels Dr. John Watson in several ways.
The address appears as part of the show's literary pattern rather than as a claim that House lives in London. House is based in New Jersey, and the fictional hospital Princeton-Plainsboro is also located there. The apartment number is therefore an easter egg that links a modern medical detective to the original detective tradition.
Viewers may remember 221B chiefly as Holmes's address, which can make the House M.D. detail easy to overlook. In the series, it identifies House's apartment and reinforces the show's recurring Sherlock Holmes inspiration.