Abstract  A teaching programme is reported in which criticalthinking skills (in the sense of reasonedjustification of arguments; see Kuhn, 1991, 1993) weretaught. The principal aims of the study were todevelop, implement and evaluate a programme forteaching evidence-based justification to vocationaleducation students in Further Education colleges. Teaching was via modelling and peer-based critiquingexercises in the context of the students'' projectwork. Eighty-four Further Education college studentsunderwent a 10-session teaching intervention whichdovetailed with their Additional Assessmentintegrative project work. Students took part inpeer-based exercises in which they learned to critiqueimaginary examples of project outlines and plans,followed by similar peer-based critiquing of eachothers'' proposed projects. Analysis of the students''dialogues with each other indicated that they hadlearned the importance of justifying arguments, andcontent analysis of their written work indicated thatthey engaged in justification of their arguments to asignificantly greater degree than control groups. Several key variables in the dialogues correlatedpositively with justification in the written work,suggesting that the dialogue had impacted on thewritten work. However, justification tended to be ofa weak kind (using anecdotes or experience-basedgeneralisations), and strong (i.e. formalresearch-based) evidence remained relativelyinfrequent and sometimes inappropriately used. Apsychometric test of general critical thinking skillsshowed no evidence of transfer of learning.