Reproductive effort affects body reserves and subsequent ability to reproduce. In fact, the energy costs of gestation and lactation in hinds of red deer have a marked effect on maternal condition. The objectives of this study were to examine the development of hind monthly body condition during gestation in relation to reproductive rest, age and age class, just as its effects on total milk yield and calf birth weight. Eighty hinds of Iberian red deer were used as subjects during 2 years of study. They had ad libitum access to food and water. Animals were weighed weekly, and body condition was individually assessed. Milking was carried out under anesthesia with a milking machine followed by hand milking to collect the remaining milk. Age and reproductive rest influenced body condition, improving with age (coefficient: 0.10+/-0.01; P<0.001) and reproductive rest (mean+/-SEM, 3.75+/-0.05 vs. 3.25+/-0.02, with and without rest respectively; P<0.001). Hind age correlated positively with her body condition (R=0.62, P<0.001), however, when age class was included in the model, age was not significant. The greater the age class (up to age class 4) the greater the body condition; however, hinds of age class 5 had a lower body condition, but no significant differences were observed. Development of the body condition during gestation was different to age class 1 with respect to the others, just as between hinds that rested the preceding year and those that did not.