The European Food Safety Authority (EFSA) asked the Panel on Plant Protection Products and theirResidues to provide guidance on methodology for performing probabilistic dietary exposureassessment of single or multiple active substances, as a potential additional tool to supplement orcomplement the standard deterministic methodologies which are currently used in the EU forconducting dietary exposure assessments for pesticides.Specific guidance is provided for basic assessments but not for refined assessments, where specialisedexpertise is required to select methods appropriate to the assessment in hand.The guidance includes probabilistic methods for quantifying some of the major sources of variabilityand uncertainty affecting dietary exposure to pesticides. Other important sources of variability anduncertainty might be quantified probabilistically in refined assessments but are addressed more simplyin basic assessments by conducting alternative model runs with optimistic and pessimisticassumptions.Guidance is provided on problem formulation, including definition of appropriate scenarios for acuteand chronic exposure assessment in the differing contexts of approval of new substances, MRLsetting, authorisation of products, evaluation of residues found above the MRL, and annual reviews ofresidue monitoring data.Detailed guidance is provided on methodology for probabilistic modelling of acute and chronicexposures and for quantifying variability and uncertainty in food consumption and residues. For basicprobabilistic assessments, optimistic and pessimistic assumptions are used for the effects of processingand for residues below the level of reporting.A separate section is devoted to additional approaches required for modelling exposure to multiplesubstances (cumulative assessment): the use of relative potency factors to cumulate exposures todifferent substances, and a basic methodology for addressing gaps in data on the co-occurrence ofresidues of different substances.Specific guidance is provided on the types and formats of outputs that should be produced from aprobabilistic assessment. Particular emphasis is placed on characterising the upper tail of the exposuredistribution and on 'drill down' techniques to evaluate the reliability of the estimates.A general approach is recommended for evaluating uncertainties affecting the model outputs. Anappendix to the guidance describes uncertainties associated with the methodology recommended inthis guidance, and provides a general evaluation of their potential impacts on estimated exposures.The guidance also includes a checklist of key issues to be considered when writing or peer-reviewingreports on probabilistic exposure assessments, a discussion of approaches to validating probabilisticassessment approaches, and a list of desirable characteristics of software for probabilistic exposuremodelling. Some comments are provided on the interpretation of results, while recognising that riskmanagement is outside the remit of EFSA.Case studies are included in an appendix, illustrating some but not all of the recommendedapproaches.Further work will be required to make the methods in this guidance available to end-users in morepractical form, including software and more specific user instructions. Some recommendations on thisare provided.