Determination of the longitudinal structure function $F_{L}$ at HERA
  Recent results from the HERA experiment H1 on the longitudinal stucture function $F_{L}$ of the proton are presented. They include proton structure function analyses with particular emphasis on those kinematic regions which are sensitive to $F_{L}$. All results can be consistently described within the framework of perturbative QCD. 
N. Gogitidze (on behalf of the H1 and ZEUS collaborations)