For C programs, flow-sensitivity is important to enable pointer analysis to achieve highly usable precision. Despite significant recent advances in scaling flow-sensitive pointer analysis sparsely for sequential C programs, relatively little progress has been made for multithreaded C programs. In this paper, we present FSAM, a new Flow-Sensitive pointer Analysis that achieves its scalability for large Multithreaded C programs by performing sparse analysis on top of a series of thread interference analysis phases. We evaluate FSAM with 10 multithreaded C programs (with more than 100K lines of code for the largest) from Phoenix-2.0, Parsec-3.0 and open-source applications. For two programs, raytrace and x264, the traditional data-flow-based flow-sensitive pointer analysis is unscalable (under two hours) but our analysis spends just under 5 minutes on raytrace and 9 minutes on x264. For the rest, our analysis is 12x faster and uses 28x less memory. Categories and Subject Descriptors...