The commonly used test to evaluate naming ability in multiple sclerosis (MS) is the Boston Naming Test (BNT). In previous studies the BNP has not shown any specific deficit in MS patients. The BNT score is obtained by adding spontaneously correct answers to correct answers obtained after semantic and phonological clues are given. Our hypothesis was that due to a lexical access deficit based on executive dysfunction, MS patients would need more clues than control subjects to normalize their performances,. Fifteen relapsing-remitting (RR) and 17 secondary progressive (SP) MS patients, and 32 controls matched for sex, age, and educational level, took the BNT. The 32 MS patients also took the BCCog (Short French battery used in MS to evaluate cognitive functions) in order to evaluate their executive functions. MS patients needed significantly more clues than matched controls to normalize their performances (P <0.001). This lexical access deficit was more frequent in the SP than in the RR group (P <0.05). A lexical access deficit inducing a denomination problem has thus been shown in MS patients. Further research should aim to better evaluate the executive functions of patients with a lexical access deficit.