This work presents the results of a survey carried out among Brazilian calibrationlaboratories accredited under ISO/IEC 17025:2005 with the objective to identify how theselaboratories investigate the root causes of unsatisfactory results in proficiency testing.The survey was coordinated by the Brazilian accreditation body, the General Coordinationfor Accreditation (Cgcre), of the Institute of Metrology, Quality and Technology(Inmetro).