The coefficient of genetic variation of fertility traits is of a similar magnitude to that present in production traits, however traditional measurements of fertility have low heritability (h2 < 0.05), and recording is often poor, hindering the identification of genetically superior animals. The effect of sire on daughter fertility has been examined as part of a DEFRA LINK project to produce an UK fertility index. The project is investigating the use of six currently recorded traits to calculate sire genetic merit for fertility: calving interval (CI), interval to first service (DIMFIR), nonreturn rate 56 (NR56), number of services per conception (CINSOBS), milk yield and condition score (Wall et al., 2002). An alternative way to measure fertility is to use endocrine measurements such as interval to commencement of luteal activity postpartum (CLA). This parameter is less influenced by management decisions and has a moderate heritability (0.16; Royal et al., 2002a.) and is measurable early in lactation. Although information on the genetic relationships between CLA and other traits of economic importance have been reported previously (Royal et al., 2002a.; Royal et al, 2002b.) further information would be useful in order to assess the usefulness of incorporating CLA into a future UK breeding programme. The objective of these analyses was therefore to obtain information on the genetic correlation (rA) between lnCLA and the emerging UK national fertility proofs.