Hi I am using the getGene function (biomart package) with a vector of ID : ex : getGene(id = refSeqIDs, type = "refseq", mart = martObj) It works with a vector length of 500 but with a length of 5000 it return NULL. Besides the vector i need to use has a length of 18000. Is there any limit for the length of the vector ? Thanks for your help. TM -- MOUROT Tabar? Stagiaire Master Pro BioInfo Plateforme transcriptome Institut de G?nomique Fonctionnelle 141, rue de la Cardonille 34094 Montpellier Cedex 5 Tel : +33 (0)4 67 14 29 64 E-mail : tabare.mourot at igf.cnrs.fr -- Passerelle antivirus IGF --