Gibberellins (GAs) are involved in a wide range of plant developmental processes. The biosynthetic pathway is discussed in Chapter 1 but it should be noted here that of all the plant hormones the GAs represent perhaps the most diverse group, with currently 125 different structures known. This diversity compounds the analysis of GAs in that not only must extraction ensure quantitative recovery of all the types, but these need to be resolved following partial purification. Moritz and Olsen (1 ) have described the analysis of GAs from milligram amounts of plant tissues.