This document defines a C language application program interface to the lightweight directory access protocol (LDAP). The LDAP API is designed to be powerful, yet simple to use. It defines compatible synchronous and asynchronous interfaces to LDAP to suit a wide variety of applications. This document gives a brief overview of the LDAP model, then an overview of how the API is used by an application program to obtain LDAP information. The API calls are described in detail, followed by an appendix that provides some example code demonstrating the use of the API.