This guide presents an updated and extended version of the ELEFAN 0, ELEFAN 1 and ELEFAN 2 programs for Electronic LEngth Frequency ANalysis. These programs can be used to estimate the parameters of a (seasonally oscillating) growth equation, total mortality (Z = P/B ratio) and related parameters, as well as to derive seasonal patterns of recruitment. Input data are length frequency samples collected at regular or irregular intervals, and, optionally, growth informations obtained from tagging-recapture experiments or from ageing studies. The revised programs incorporate modifications suggested by recent simulation studies aimed at identifying sources of the bias in the original ELEFAN procedures. The programs are written in Microsoft Basic and available in a CP/M version (8 bit CPU Zilog Z80), in a MS/DOS version (16 bit CPU Intel 80xx), and in the next future in a CP/M 68K version (16/32 bit CPU Motorola 68000). The listings included here refer to the MS-DOS version of ELEFAN.