Extraction of the aerial parts of Achilles ligustica furnished the known guaianolides matricarin, chrysartemin A and chrysartemin B, a new guaianolide isoapressin, the flavones nevadensin, 3,6-dimethoxy-5,7,4' trihydroxyflavone and quercetagetin 3,6,7-trimethyl ether and (+)-E-2,6-dihydroxy-2,6-dimethylocta-3,7-diene.Representatives of the genus Achillea (Compositae. Anthemideae) chracteristically furnish sesquiterpene lactones of the guaianolide type. Our recent work on AchiL lea ligustica All., a species which occurs in the Mediterranean region, tends to confirm this generalization. Isolated were the known guaianolides matricarin (l), chrysartemin A (2) and chrysartemin B (3) as well as nevadensin (5,7-dihydroxy-6,8,4'-trimethoxyflavone), 3,6-dimethoxy-5,7,4'-trihydroxy flavone and quercetagetin 3,6,7-trimethyl ether. A new guaianolide was 4a which, because of its relationship to 4b (apressin) from Achilleq depressa [l] we have named isoapressin. The monoterpene (+)-E-2,6-dihydroxy-2,6-dimethylocta-3,7 diene (5) of uncertain absolute configuration was also found.Structure and stereochemistry of 4a were established from the 'H NMR spectrum (Table 1) using extensive decoupling which will not be described in detail and NOE studies. (Table 2). Most chemical shifts, couplingconstants and the facile loss of oxygen in the CIMS paralleled earlier observations in the case of apressin (4b) [l] with one exception-the presence of a doublet at 62.30 (J= 1.5 Hz) coupled to H-9 (ddd at 65.02). After exchange with D,O the signal at 62.30 disappeared and the H-9 signal collapsed to a doublet. Hence the acetate function was attached to C-10, as is also indicated by the downfield shift of H-14, and the free hydroxyl was at C-9. Irradiation of H-6, H-9 and H-15 caused enhancements in the signals of H-2 and H-3, hence the olefinic bridge was b-orientated, the significant NOES observed between H-6 and H-9, between H-9 and H-15 and between H-5 and H-7 showed that the protons involved were synrelated. The negative Cotton effect ( [KJZ5, -2350) shows that the relative configuration shown in formula 4a represents the absolute configuration as well. Finally, the data provided in the Experimental established the structure of (+)-5, although the absolute configuration remains unknown.