Studies on vocabulary acquisition in second language learning have revealed that a large amount of vocabulary is learned without an overt intention, in other words, incidentally. This article investigates the relevance of different lexical processing strategies for vocabulary acquisition when reading a text for comprehension among 24 advanced learners of French who are native German speakers. The strategies which these learners used to cope with unknown lexical items were analysed with regard to the cognitive operations involved. The features of the different processes that lead to retention of new vocabulary are discussed based on introspective data gathered during the reading process and on the results of a subsequent vocabulary test. Examining how provisional lexical entries in the mental lexicon are created facilitates the discussion of an important question about the relevance to vocabulary acquisition of implicit processing of information on the one hand versus active, elaborate, and explicit processing on the other. The results provide evidence for the achievement of implicit processes and additional information concerning differential depth of processing.