Abstract: Abstract: In the first part of the talk, I will focus on Quantum Hall Effect (QHE) in graphene p-n junctions, which has been recently demonstrated experimentally. I will explain the observed conductance quantization which is fractional in the bipolar regime and integer in the unipolar regime in terms of QH edge modes propagating along and across the p-n interface. In the bipolar regime the electron and hole modes can mix at the p-n boundary, leading to current partition and quantized shot noise plateaus similar to those of conductance, while in the unipolar regime transport is noiseless. In the second part of the talk, I will discuss unusual nature of nu=0 QHE state in graphene and show that electron transport in this regime is dominated by counter-propagating edge states. Such states, intrinsic to massless Dirac quasiparticles, manifest themselves in a large longitudinal resistivity rho_xx h/e^2, in striking contrast to rho_xx behavior in the standard QHE. If time allows, I will also discuss the effect of Coulomb interaction on the counterpropagating edge states, and show that it leads to Luttinger liquid behavior.