Abstract. The effects of time after birth and of twinning on rectal temperature (RT), heart rate (HR), respiratory rate (RR) and body weight (BW) values were evaluated in five singleton Comisana lambs (three males and two females), five singleton Maltese Kids (three males and two females), four couples of twin Comisana lambs (four males and four females) and four couples of twin Maltese kids (four males and four females) during the first month of life. For all kids and lambs, RT, HR, RR and BW were recorded after 1 and 24 h from birth and every 2 days until the 30th day of life. The application of two-way repeated measures analysis of variance (ANOVA) showed a statistically significant effect of time (P < 0.0001) on RT, HR, RR and BW values in all lambs and kids during the first month of life. Any significant effect of twinning (P > 0.05) on all studied parameters was found in lambs, whereas statistically significant differences in BW, RT and HR values (P < 0.01) were found between twin and singleton kids throughout the first month of life. The results obtained in this study make a contribution to the knowledge of homeostatic, cardiorespiratory and thermoregulatory adaptations occurring in singleton lambs and kids and in twin lambs and kids during the first 30 days of life. Our findings indicate that the BW, RT, HR and RR values, whose homeostasis is still evolving in newborn, should be interpreted dynamically as a function of the period of postnatal adaptation and also of twinning.