. Constructing an infinite family of binary cyclic codes with good parameters is an interesting topic. The objective of this paper is to construct several families of binary cyclic codes with a square-root-like lower bound. An infinite family of binary cyclic codes of length 2m - 1 and minimum distance m & RightFloor; + 2 is presented. Several infinite families of binary duadic codes with variable length and have a square-root-like lower bound are constructed. As a by-product, several families of binary self-dual codes with a square-rootlike lower bound are presented. These families of binary cyclic codes contain optimal linear codes.