By means of sequence analysis, murine fetal antigen 1 (mFAl) isolated from Mus musculus amniotic fluid was shown to be the circulating protein of the δ‐like protein, stromal‐cell‐derived protein 1 (SCP‐1) and preadipocyte factor 1 (Pref‐1) gene products. The protein contains 36 cysteine residues arranged in six epidermal‐growth‐factor‐like domains. The purification of several C‐terminal peptides of varying lengths showed mFA1 to be C‐terminal heterogeneous. O‐linked glycosylations of the NeuNAcα2–3Galβ1‐ 3(NeuNAcα2–6)GalNAc type were present on all C‐terminal peptides at residues Thr235, Thr244 and Thr248, although glycosylation on Thr244 was only partial. Three N‐linked glycosylations were localized in mFA1 (Asn77, Asn142 and Asn151), two of which (Asn142 and Asn151) were in the unusual Asn‐Xaa‐Cys motif. Fucosylated biantennary complex‐type and small amounts (less than 5%) of triantennary complex‐type structures were identified on the glycosylated asparagine residues using sequential exoglycosidase and endoglycosidase digestions combined with matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐MS). The presence of O‐linked monosaccharides (glucose attached to Ser71, Serl93 and fucose at Thr201) was tentatively ascertained by combining Edman degradation and MALDI‐MS. The results presented shows mFA1 to be the circulating heterogeneous cleavage products of the membrane‐bound protein encoded by the murine cDNAs dlk, pref‐1 and SCP‐1.