Guinea pigs are used for meat production in South America, Africa, and Asia. The increased interest in this product is due to the low production price, and because of their relatively rapid reproduction and the large litter size. The objective of the present study was to evaluate the effect of age and sex on weight, yield, drip loss and pH evolution in guinea pig carcasses. Forty guinea pigs (10 male and 10 female of 3 mo age, and 10 male and 10 female of 12 mo age discarded animals) were used. The animals were fasted during 14 h before slaughter. Live weight at slaughter (LWS), empty body weight (EBW), and hot and cold carcass weights (HCW and CCW) were recorded. pH evolution was measured at 15, 45 min and 24 h after slaughter in Longissimus dorsi (LD) and Psoas major (PM) muscles. Four different carcass yields and drip loss (in grams and percentage) were calculated. Twelve mo-age animals showed higher LWS, EBW, HCW and CCW than 3 mo-age guinea pigs. The lowest values of hot or cold carcass yields (HCY, CCY) were observed in 3 mo-age male guinea pigs and no differences were found among the other groups. CCY was lower than HCY in all cases, due to the drip loss during the chilling time (24h at 4°C). When yields were presented related to empty body weight, the values were higher than the yields that used live weight at slaughter, as expected. Discarded animals had higher drip losses, but expressed in percentage, 3 mo-age females had the highest losses, while the 12 mo guinea pigs showed the lowest losses. pH declined significantly during 24h in both muscles and all the animals, with the exception of 12 mo-age female guinea pigs. At 15 and 45 min LD did not show differences due to sex or age. After 24h, 12 mo-age females had the highest pH values (6.37) and 3 mo-age females had the lowest (5.54). When pH in PM was analyzed, the results revealed different behavior than LD. At 15 min and 24 h, 12 mo females presented the lowest pH (6.29 and 6.30, 15 min and 24 h, respectively), while the in the other groups pH ranged from 6.70 to 6.44 at 15 min, and was near to 6 after 24h postmortem.