Linear carcass measurements (LCM) are important variable of carcass quality. Several studies describe a relationship between LCMs and body live weight and other parameters of carcass and meat quality in different species. Guinea pigs are an important source of protein in numerous undeveloped countries and currently they are introducing in developed countries. The present study analyzes the effect of sex and fattening or discarded guinea pigs on LCMs carcass. Forty guinea pig carcasses after 24 h of chilling were selected: 20 from 3months-age fattening animals (10 males and 10 females) and 20 from 12 mo-age breeding discarded animals (10 males and 10 females). The following measurements in carcasses after chilling for 24 h at 4°C were recorded: carcass length (L), loin length (Lo), hind limb length (F), width of the buttocks (G), lumbar circumference (LC), thorax circumference (ThC) and thorax width (ThW). Furthermore carcass compactness (CarC) and leg compactness (LegC) were calculated. L, Lo, LC and ThC were higher in 12 mo-age than 3 mo-age guinea pigs. Sex did not affect the described measurements, and G values were similar (7 cm) in all studied animals. F was higher in 12 mo-age males (12 cm), while 3 mo-age females showed the smaller value (9 cm). There was a sex effect on F for 12 mo animals, being higher in males than in females (12 vs 10 cm, respectively). When CarC was analyzed an age effect was evident in 12 mo-age animals, which showed 40g cm-1 of carcass weight vs 25–30g cm-1 for the 3 mo-age guinea pigs. So, after 3 mo the animals not only increased their length, but they also increased their body mass. Sex had an important effect on LegC of fattening guinea pigs: males had higher values than females (67% and 55%, respectively). However, in discarded guinea pigs, males showed smaller compactness than females (50% and 60%, respectively).