Gregory House’s apartment address in House M.D. is 221B, echoing Sherlock Holmes’s famous address at 221B Baker Street. The connection is one of the show’s clearest references to its literary inspiration.
House and Holmes share more than an address. Both are exceptionally observant problem-solvers who use deduction to solve difficult cases, and both have close companions who document or interpret their behavior. House’s friend James Wilson parallels Dr. John Watson in several aspects.
House’s name also resembles Holmes’s surname in its brevity and sound pattern, while the series frequently frames medical diagnosis as detective work. These parallels are inspirations rather than claims that House is a direct adaptation of every Holmes story.
221A is a nearby-sounding alternative, but the famous Holmes address is 221B Baker Street. The fictional House apartment reference is generally presented as 221B, without requiring a full street address in the question’s answer.