We prove several new results regarding the relationship between probabilistic time, BPTime (t), and alternating time, ΣO(1)Time (t). Our main results are the following: 1. We prove that BPTime (t) ⊆ Σ3Time (t · poly log t). Previous results show that BPTime (t) ⊆ Σ2Time ( t2 · log t ) (Sipser and Gács, STOC ’83; Lautemann, IPL ’83) and BPTime (t) ⊆ ΣcTime (t) for a large constant c > 3 (Ajtai, ...