The Chemistry Didactic Unit is composed of permanent members and of teaching assistants who are responsible for the training in first and second years (chemistry exercise and laboratory). Its main objectives are : - to coordinate and harmonize the formal teaching with exercises and experiments. - to follow the students personnally to help them as soon as difficulties arise and therefore to decrease the failure rate in first year or to help them to reorient. - to give the students the opportunity to refresh the essential chemical knowledge which has to be mastered to begin a fisrt year in Sciences or Medicine (preparatory sessions held in August).