Practicing retrieval on previously studied materials can potentiate subsequent learning of new materials. In four experiments, we investigated the influence of retention interval and lag on this test-potentiated new learning (TPNL) effect. Participants studied four word lists and either practiced retrieval, restudied, or completed math problems following Lists 1–3. Memory performance on List 4 provided an estimate of new learning. In Experiments 1 and 2, participants were tested on List 4 after either a 1 min or 25 min retention interval. In Experiments 3 and 4, participants took at 25 min break before studying List 4. A TPNL effect was observed in all experiments. To gain insight into the mechanism that may underlie TPNL, we analyzed the extent to which participants organized their recall from list to list. Relative to restudy and math, testing led to superior semantic organization across lists. Our results support a strategy change account of TPNL.