In this paper, we analyze the L2-gain of sampled-data systems with asynchronous sensing and control. The closed-loop system has time-varying clock offsets and sampling intervals and can be modeled as a parameter-uncertain system. We use a lifting approach and a gridding and norm-bounded approach in order to analyze intersample behavior and deal with parameter uncertainty, respectively. An upper bound on the L²-gain is derived via linear matrix inequalities. We illustrate the proposed method by applying it to an active suspension system.