Most portable software is written in a standard high-level language such as Fortran or Cobol. However, merely using a high-level language does not guarantee portability. Possible problems with the portability of programs written in high-level languages are considered in general terms here, while problems specific to particular high-level languages are discussed in later chapters. In this chapter we discuss the importance for portable programming of language standards and of various kinds of software aids. General guidelines for portable programming in high-level languages are also suggested.