Parton distribution functions (PDFs) are crucial ingredients for measurements at hadron colliders, since they describe the initial states and therefore critically impact the precision of cross section predictions for observables. It is however possible to constrain the PDFs and to improve the precision of the prediction using LHC data.
This talk will review some areas, where the PDFs play an important role for the cross section measurements and then talk about the inclusion of current ATLAS measurements in PDFs. Particular emphasis will be given to the determination of the strange content of the proton.
