Neutrinos have remained elusive but in the limelight for so many years. Recent results indicating the presence of non-zero neutrino mass by the super-Kamioka detector was the latest event which caught attention of the general physics community as well as of specialists working in high energy physics.

This special issue of Pramana is aimed at summarizing these recent developments in the field of neutrino physics. We have included in this issue reviews covering different aspects of neutrino physics. The articles contained in the issue give introduction to the solar and atmospheric neutrino problems and review their current status. Also included are reviews summarizing different theories of neutrino masses in the light of recent experimental results. In addition, the present volume also includes summary of some aspects of cosmology and astrophysics which can have significant influence on the neutrino masses and theories describing them.

We are grateful to all the contributors to this volume for sparing their time to write these reviews. Some of the articles contained in the review are updated versions of the talks given at the `Discussion Meeting in Neutrino Physics' held at the Physical Research Laboratory, Ahmedabad during February 2-4, 1999. We thank the participants of this meeting for lively discussions, some part of which is captured here through the articles. Our special thanks go to Saurabh D Rindani, who was the organizer of the conference along with one of the editors of the present volume (ASJ). We are also grateful to the Editorial Board of Pramana, specially, H R Krishnamurthy and R Godbole for giving us an opportunity to edit this volume and the Pramana editorial office for their efforts in bringing it out.

Anjan S Joshipura

Theory Group, Physical Research Laboratory

Ahmedabad 380 009

and

Palash B Pal

Theoretical Nuclear Physics Division

Saha Institute of Nuclear Physics, Calcutta 700 064

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