This chapter defines important considerations in the use of condition indices as applied to marine fish larvae, and describes the present state of knowledge concerning each index. An appraisal of their relative merits is then attempted by comparing the strengths and limitations of each category. Measures of condition integrate feeding success over time, and give an indication of the probability of starvation and survival. This chapter explores that, the central purpose of measuring condition is to predict reliably survival probabilities under given food regimes in order that observed larval abundances can be used as early predictors of recruitment. The chapter illustrates that, future research on condition indices is likely to be more productive if it is devoted to the refinement of existing methods, rather than to search for the ideal condition index. The chapter concludes by providing suggestions for the use of condition indices in different situations and identifies topics requiring further research. © 1994, Academic Press Limited