Papaver somniferum plants accumulate the secondary products codeine and morphine. P. bracteatum accumulates their precursor, thebaine. The aims of the project were to use tissue cultures for the production of these alkaloids and for the biotransformation of thebaine to codeine and morphine. Methods were evaluated for the extraction, separation and quantification of mg or mug amounts of morphinan alkaloids from plant material. TLC, IIPLC and RIA were useful. Poppy cells fron a range of seed sources and explants were grown in static and suspension culture. Manipulations were made in atterpts to induce morphinan biogenesis. These included inmobilisation of cells and changes in the growth medium. Morphinans were absent from unspecialised cells in all but one instance. The biotransformation of thebaine was tested in cell suspensions of P. somniferum and Nicotiana alata. Using thebaine (biosynthesised from CO2) these experiments were extended to organs of the P. somniferum plant. A thebaine-biotransfomation product arose in N. alata (but not P. somniferum) suspensions that also arose in excised P. somniferum capsules. A non-specific enzymic activity is proposed. No codeine or morphine were produced. Plant regeneration was demonstrated, in good yield, by embryogenesis fron meristenoid tissue of P. bracteatum. In P. somniferum the process was initiated but was not routinely successful. Regeneration may be useful for plant improvenent via cloning or as a source of variation. On reorganisation into plantlets, capacity for morphinan alkaloid accumulation was realised. Capacity for alkaloid accumulation is discussed in tenns of a requisite minimum level of cytodifferentiation, perhaps of laticifer-like cells. The uptake or binding of radiolabelled morphine by suspension cultures was investigated, since binding may be a reason for failure to detect morphinans in cultures extracted by the usual methods. Evidence was found that exogenous morphine binds to an insoluble fraction in P. somniferum and I. tabacum but cells did not contain any endogenous bound morphincins.