The Boston 2 Big Sur Challenge is a real, official program — not an informal tradition runners invented on their own — that pairs an entry in the Boston Marathon with an entry in the Big Sur International Marathon roughly a week later. It's built for a specific kind of runner: someone who has already qualified for and entered Boston and wants to test what back-to-back marathons on opposite coasts actually feels like. This guide explains how the program works, not how the two courses compare.

The basic format

Boston is held on a Monday in April under the Boston Athletic Association's own scheduling, and Big Sur follows on the Sunday roughly a week later on this race's own recurring late-April date — which has historically meant anywhere from about six days to just under two weeks between the two races, depending on how the two organizations' calendars line up in a given year. Runners who complete the Boston 2 Big Sur Challenge run both marathons within that window, and the program has been part of Big Sur's race weekend for well over a decade at this point, introduced specifically as a category for the fittest, or most stubborn, runners willing to attempt it.

How you qualify

Eligibility for the B2B category is straightforward but non-negotiable: you have to already be an official entrant in that year's Boston Marathon. It doesn't matter how you got into Boston — a qualifying time, a charity entry, or another accepted pathway all count — but Big Sur's program has no official connection to Boston's own registration and doesn't include or guarantee a Boston entry. You'll need to secure that separately, through Boston's own process, before B2B registration is worth pursuing.

Registering for the challenge

Registration for the Boston 2 Big Sur category opens separately from, and later than, Big Sur's general random drawing, and runners don't need to go through that drawing at all — B2B is its own first-come, first-served entry path once it opens. It's worth noting this is a distinct fee on top of whatever Boston itself costs, and the two registrations are handled entirely independently by their respective organizers.

What finishing both earns you

Runners who complete both races within the eligible window receive recognition specific to the challenge: a distinct finisher's medallion for the B2B category, a jacket, and other B2B-branded gear beyond what regular Big Sur finishers get, along with a dedicated post-race recovery area at the Big Sur finish line. There's also an awards structure specifically for the challenge, recognizing the fastest combined times across both races in open and masters categories, separate from each race's own overall results. One important catch: if you're registered for B2B but don't start or finish Boston, you lose eligibility for the challenge-specific recognition, even if you go on to run Big Sur.

The real challenge is recovery

The logistical and physical core of B2B isn't really about pace on either course — it's about what happens in the days between them. Runners attempting the double are, in effect, racing a marathon on tired legs well inside two weeks after racing one already, often while also managing cross-country travel from New England to California's Central Coast in between. Experienced B2B finishers consistently describe the second race as being run largely on feel and recovery management rather than goal pace, which is worth internalizing before you commit: the honest goal for most B2B runners at Big Sur is finishing strong, not chasing a personal best on a course that's demanding even on fresh legs.

Not a recent gimmick

The challenge itself isn't a recent gimmick. Big Sur introduced the Boston 2 Big Sur category well over a decade ago, and it has run in most years since, building a small but dedicated community of repeat "double" finishers who treat it as its own distinct achievement separate from either race individually. It's also worth understanding what the program is not: it isn't an official Boston Athletic Association event or partnership, just a category Big Sur itself created and administers for runners who happen to be doing both races. That distinction matters mainly for expectations — your Boston experience is entirely standard, and the "challenge" framing, medallion, and recognition all live on the Big Sur side of the double.

If a back-to-back double isn't for you but you're still building out a marathon calendar, RaceRove's marathon listings are a good place to keep exploring.