By an algebra Λ we mean an associative k-algebra with identity, where k is an algebraically closed field. All algebras are assumed to be finite dimensional over k (except the path algebra kQ). An algebra is said to be biserial if every indecomposable projective left or right Λ-module P contains uniserial submodules U and V such that U+V=Rad(P) and U∩V is either zero or simple. (Recall that a module is uniserial if it has a unique composition series, and the radical Rad(M) of a module M is the intersection of its maximal submodules.) Biserial algebras arose as a natural generalization of Nakayama's generalized uniserial algebras [2]. The condition first appeared in the work of Tachikawa [6, Proposition 2.7], and it was formalized by Fuller [1]. Examples include blocks of group algebras with cyclic defect group; finite dimensional quotients of the algebras (1)–(4) and (7)–(9) in Ringel's list of tame local algebras [4]; the special biserial algebras of [5, 8] and the regularly biserial algebras of [3]. An algebra Λ is basic if Λ/Rad(Λ) is a product of copies of k. This paper contains a natural alternative characterization of basic biserial algebras, the concept of a bisected presentation. Using this characterization we can prove a number of results about biserial algebras which were inaccessible before. In particular we can describe basic biserial algebras by means of quivers with relations.