Human lipocortin (annexin) 1, a member of the annexin family of phospholipid binding proteins, has previously been expressed in E. coil (Huh et al., 1990). To improve the expression level of lipocortin 1 in E. coli, several expression vectors containing either the P-L or the P-trc promoter were constructed. The highest expression level, up to 20% of the total E. coli proteins, was obtained with plasmid pHT3. Plasmid pHT3 contains the pUC origin, the lipocortin 1 cDNA under P-trc promoter, and the lacI gene.