A review is given of a selection of papers published in the past year in this rapidly expanding field. Such papers may be divided into four groups: (i) those in which ring-closing metathesis (RCM) has been used as a key step in the total synthesis of a natural product: (R)-(+)-lasiodiplodin, dactylol, (-)-stemoamide, and epothilone A; (ii) those in which RCM has been used to make a sub-unit of a natural product: the marine toxins brevetoxin B, brevetoxin A, and maitotoxin; (iii) those in which RCM has been used to make compounds of known biological activity: fluvirucin B-1 (Sch 38516); (iv) those in which metathesis reactions have been used to make compounds of potential synthetic importance: crown ethers, aza sugars (polyhydroxylated pyrrolidines), beta-lactams, chromenes, and aminoacids. The catalysts used have been one of the following four metal carbene complexes: the Schrock catalyst Mo(=CHCMe2Ph)(=NC6H3-2,6-i-Pr-2)[OCMe(CF3)(2)](2;) Grubbs catalysts Ru(=CHCH=CPh2)Cl-2(PCy3)(2) and Ru(=CHPh)Cl-2(PCy3)(2), where Cy - cyclohexyl; and the Tebbe reagent which behaves as Ti(=CH2)Cp-2, where Cp = cyclopentadienyl. In this paper these are denoted by Mo-1, Ru-l, Ru-2, and Ti-l, respectively. Ti-l is especially useful for effecting RCM by the carbonyl-olefination reaction, while the RCM of enynes, catalyzed by Ru-2, is another valuable metathesis reaction. (C) 1998 Elsevier Science B.V. All rights reserved.