Some researchers have argued that short-term memory (STM) deficits are due to overly rapid loss of activation of the nodes in the lexical-semantic system. The current study investigated the activation and decay of semantic representations for a patient (ML) with a semantic STM deficit using a semantic priming paradigm. Experiment 1 used a traditional paired presentation task to examine priming at two SOAs (350ms & 900ms). Experiment 2 and 3 used a single presentation task to reduce the use of strategies at long SOAs. ML demonstrated normal priming effects at short and long SOAs when priming primarily reflected automatic spreading activation. The results suggest that ML has normal activation and decay in the lexical-semantic system and support a model with STM buffers separate from the lexical-semantic system. Experiment 4 explored ML and older control subjects' use of strategies in a priming task. The sources of ML's STM deficit were discussed.