This work was carried out to compare the endocrine function of ovarian tissue isolated in vitro, in an identical environment between ewes and ewe lambs. Furthermore, to determine whether the differences in endocrine and reproductive function of ewes and ewe lambs are related to differences in the proteomics of corpora lutea, follicles and oocytes. Oestradiol concentrations in tissue cultured in TCM-199 were similar for ewe and ewe lamb follicles collected post slaughter on day 9 to 12 of the oestrous cycle and cultured for different incubation times but increased with increase in follicular size. Oestradiol secretion was greater (P<0.001) for ewe and ewe lamb follicles cultured in media with FCS. Media progesterone concentrations were higher (P<0.001) for ewe than ewe lamb follicles. Progesterone in media and in follicular fluid was increased with increased follicles size. Ewe CL, collected on day 9 to 12 of the oestrous cycle, produced more progesterone than ewe lamb CL when cultured in TCM-199 with or without FCS, PVA, BSA. Proteomics indicated more large spots, in ewe follicular and CL tissue average gels compared with ewe lamb average gels. The protein spots were estimated to be between 45 to 97 kD, in both tissue and age groups, this range of molecular weight could have affected steroid hormone synthesis. (Chapter.3). Ewe and ewe lamb follicles cultured with FSH and LH produced more oestradiol than without, furthermore, oestradiol concentration increased with follicle size. There was no difference in media oestradiol concentration between age groups after 24 h of culture. However, for follicles cultured for 2, 4 or 6 h, concentrations were greater after 4 and 6 h, in ewes than in ewe lambs. Overall ewe lamb follicles produced more progesterone (P<0.001) than ewe follicles when cultured with FSH and LH when cultured for 24 h, but no difference was observed after 2, 4 and 6 hours between ewes and ewe lambs Overall ewe follicles produced more (P<0.002) progesterone than ewe lambs when cultured with different concentration of hCG although there was no difference between ages with respect to oestradiol concentrations. Ewe CL secreted more progesterone (P<0.002) than ewe lamb CL, when cultured for 0 or 24 h. Furthermore, tissue concentrations were greater in ewe CL than ewe lamb CL after incubation in TCM-199, TCM-199 plus BSA, TCM-199 plus FCS and TCM-199 plus PVA. Ewe lamb CL produced more progesterone than ewe CL in medium containing LH when cultured for 2, 4 and 6 hours, but ewes produced more progesterone than lambs when CL were cultured with different concentrations of hCG. Relative to untreated shells, the protein profiles of the ewe follicular shells treated with FSH and LH changed to a greater extent than that of the ewe lambs treated gels in both ages contained more protein spots than control gels. The largest spots were estimated to be between 30 and 97 kDa (Chapter.4). There was no difference between age groups for follicles from ewes and ewe lambs treated with ovagen in oestradiol and progesterone concentrations observed after 2,4, 6 and 8 h of incubation in TCM-199. However, treatment with ovagen plus hCG resulted in higher oestradiol and progesterone concentrations in the media from ewe follicles compared to ewe lambs. Furthermore, there were more protein spots in the range 30 to 66 kDa marker in gels from ewes treated with either ovagen or ovagen plus hCG than for ewe lambs (Chapter 5). Lamb oocytes were smaller than ewe oocytes and developed to a lesser extent in culture. Furthermore, the addition of FCS to TCM-199 caused greater cytoplasmic and nuclear maturation than other media used in this experiment and ewe lamb oocytes have a similar 1D protein bands compared with ewe oocytes, but contained less protein (Chapter 6).