Researchers often assume that automatic semantic priming effects found in lexical decision tasks are due to spreading activation at a conceptual knowledge level. Recent research questions this assumption by demonstrating that automatic priming does not occur for word pairs that are semantically related but not normatively associated (e.g., Shelton & Martin, 1992). The present research investigated priming at a conceptual level by manipulating depth of prime processing which forced subjects to access semantic knowledge. To ensure the priming effects were due to automatic processing two tasks were used which were designed to lessen the likelihood that subjects would engage in strategies making use of the semantic relationship between the word pairs. The first task used a single word presentation procedure and a low proportion of related words in the stimulus set which has been shown to uncover automatic priming in a lexical decision task (Shelton & Martin, 1992). Several experiments were conducted where subjects were required to make semantic decisions about each of a sequence of words. The second task was a modified Stroop task in which subjects either processed the prime nonsemantically or semantically and named the color of a subsequent target word. Previous studies have shown that an associative relationship between the prime and target slows naming of the color of the target. It has been argued that the inhibition in this task results from automatic processing because noticing prime-target relationships would only produce greater interference. The results showed that priming was found for semantically related, unassociated word pairs in the semantic judgment tasks but not in the modified Stroop task. A final experiment demonstrated that the relatedness priming found in the semantic judgment experiments only came about when the prime-target pairs were related and the decision between the prime and target was the same. The results from the semantic judgment experiments suggest that the priming effect is due to the similarity in the information used to make the decision rather than activation of all semantic features shared between two concepts. The results from the modified Stroop task suggest there is no immediate influence of conceptual information on lexical access.