We present a polynomial-time algorithm deciding bisimilarity between a normed BPA process and a normed BPP process, with running time O(n7 ). This improves the previously known exponential upper bound by ˇCern´a, Kˇret´ınsk´y, Kuˇcera (1999). We first suggest an O(n3 ) transformation of the BPP process into “prime form”. Our algorithm then relies on a polynomial bound for a “finite-state core” of the transition system generated by the (transformed) BPP process.