This book describes work on some phase coherent phenomena seen in mesoscopic systems. Mesoscopic systems are systems in which quantum effects become apparent. Being at the borderline between the microscopic and macroscopic regimes, they are uniquely placed to be testing ground for various quantum phenomena and their absence (decoherence or dephasing) as system size increases. Indeed, decoherence, that is understanding how these quantum effects vanish due to interaction with surrounding is one of the most exciting topics of present day research. Importantly, devices which exploit quantum interference effects are being proposed. In this thesis some aspects of electron transport and quantum interference effects at mesoscopic scales are presented.