Introduction  The  multimodal  practice  of  teaching  was  studied  as  a  combination  either  of  semiotic  modes  (e.  g.  Lund,  Bécu-Robinault,  2013)  or  of  speech  and  gesture  (Alibali,  et  al.,  2014,  Goldin-Meadow,  2004,  Valenzeno,   Alibali,   Klatzky,   2003).   Studies   focusing   on   explanatory   skills   show   that   this   combination  get  more  complex  as  a  child  grows  (Colletta  &  Pellenq,  2005),  and  may  vary  depending  on  the  interactional  setting  (Mazur-­Palandre,  Colletta,  Lund,  2014).  A  common  pedagogical  practice  consists   in   asking   a   tutor   student   to   explain   something   to   younger   students.   Nevertheless,   how  these  students  manage  to  do  so  in  an  authentic  setting  is  still  unstudied.  This  paper  explores  this  issue  on  the  basis  of  videotaped  explanations  elaborated  by  senior  students  for  freshmen.Data  and  research  questionsThe   pedagogical   setting   is   an   extracurricular   activity,   held   in   the   USA   and   France,   led   by   senior  students  for  junior  students.  It  is  based  on  a  multiple‐choice  questionnaire,  and  alternates  class  and  group  discussion,  and  ‘knowledge  questions’  (KQ),  and  debate  questions.  For  KQ,  the  leader  student  has  to  explain  the  correct  answer,  with  the  help  of  an  information  slide.  We  here  study  this  specific  task,  comparing,  for  two  KQ,  three  American  and  two  French  female  leader  students. Two  research  questions  guide  our  work:  1)  how  do  these  senior  students  use  multimodal  resources  to  manage  with  the  task?  ;  2)  what  are  the  didactical  effects  of  their  strategies?  We  focus  on  three  multimodal   resources:   leaders’   speech,   their   gestures,   and   the   use   of   the   slide.   We   also   consider  their  body  and  head  orientation  to  define  their  attention  focus.Methodology:  analytical  stepsWe   first   characterize   the   use   of   multimodal   resources   for   each   explanatory   sequence.   We  investigate   three   aspects:   a)   attention   focus;   b)   amount   of   referential   gestures;   c)   use   of   gestures  serving   other   aspects   of   the   management   of   the   interaction.   We   then   define   a   typology   of  multimodal  profiles.Our  second  step  focuses  on  the  didactical  effects  of  the  identified  multimodal  strategies.  It  consists  of   an   inventory   of   the   information  provided   in   each   of   the   10   sequences,   comparing   what   is  provided  on  the  slide,  what  is  added  through  leaders’  speech,  and  what  appears  in  their  gestures.First  results  and  significance  Most  of  the  leaders  alternate  their  attention  focus  between  the  screen  and  the  audience.  Attention  to  the  screen  is  associated  with  pointing  gestures  and attention  to  the  audience  is  associated  with  representational  gestures.  Our  second  analytical  step,  still  in  progress,  already  gives  evidence  of  the  large  didactical  work  of  the  leaders,  who  provide  a  lot  of  information  that  is  not  on  the  slide.  By  the  time  of  the  conference,  we  will  be  able  to  assess  the  didactical  value  of  their  multimodal  strategies,  which  can  be  useful  to  improve  teachers’  training.