This volume is a collection of the Nobel Lectures delivered by the prizewinners, together with their biographies, portraits and the presentation speeches at the award ceremonies in Stockholm for the period 1991 - 1995. Each Nobel Lecture is based on the work for which the laureate was awarded the prize. New biographical data of the laureates, since they were awarded the Nobel Prize, are also included. These volumes of inspiring lectures by outstanding chemists and biochemists should be on the bookshelf of every keen student, teacher and professor of chemistry as well as of those in related fields.Below is a list of the prizewinners during the period 1991 - 1995 with a description of the works which won them their prizes.(1991) R R ERNST for his contributions to the development of the methodology of high resolution nuclear magnetic resonance (NMR) spectroscopy; (1992) R A MARCUS for his contributions to the theory of electron transfer reactions in chemical systems; (1993) For contributions to the developments of methods within DNA-based chemistry: K B MULLIS for his invention of the polymerase chain reaction (PCR) method; M SMITH for his fundamental contributions to the establishment of oligonucleiotide-based, site-directed mutagenesis and its development for protein studies; (1994) G A OLAH for his contribution to carbocation chemistry; (1995) P CRUTZEN, M J MOLINA & F S ROWLAND for their work in atmospheric chemistry, particularly concerning the formation and decomposition of ozone.