This book is primarily designed for senior undergraduate students wishing to pursue a course in Lattices/Boolean Algebra. It can also serve as an excellent introductory text for those desirous of using lattice-theoretic concepts in their higher studies. The first chapter lists down results from Set Theory and Number Theory that are used in the main text. Chapters 2 and 3 deal with partially ordered sets, duality principle, isomorphism, lattices, sublattices, ideals (dual, principle, prime), complements, semi and complete lattices, chapter 4 contains results pertaining to modular and distributive lattices. The last chapter discusses various topics related to Boolean algebras (lattices) including applications. Under this chapter, Boolean functions, disjunctive (conjunctive) normal forms, series parallel, non-series parallel circuits, n-terminal circuits, don’t care condition’, simplification and design of circuits are discussed. Theoretical discussions have been amply illustrated by numerous examples and worked-out problems. Hints and solutions to selected exercises have been added towards the end of the text as a further help. The second edition is richer by the presence of more examples, worked-out problems and exercises, retaining the style and flavour of the first edition.