Calving - first service (IPPS) and calving - ovulation (IPPO) intervals were determined in 128 dairy cows from 5 intensively managed farms in Lima, Peru. Progesterone levels, determined by radioinmunoassay in a total of 1450 skim milk samples taken twice weekly from 15 days post partum until first artificial insemination, were used to determine IPPO. Field data on calving number (primiparous and multiparous), calving season (Spring September-December and Summer January-April), body condition (BCS evaluated monthly starting 30 days post partum) and milk production were collected. Multiple regression analysis (GLM), with IPPO and IPPS as dependent variables, and calving season, calving number, changes in BCS, milk production, heat detection efficiency and farm as independent variables, revealed an IPPO of 45 + 19.9 days and IPPS of 99.2 + 50. l days. IPPO was influenced by calving season and farm, and IPPS by heat detection efficiency, BCS at calving and farm.