Biogeochemical prospecting (the chemical analysis of vegetation to obtain evidence of mineralization in the soil and rock beneath) has been used successfully for many years in Australasia (Nicolls et al. 1965; Brooks 1968), Canada (Warren 1962), The Soviet Union (Malyuga 1964), The United States (Cannon 1960) and several other countries. A serious shortcoming of some of the earlier work is that it has not always had a sound statistical background, the suitability of a given species for biogeochemical prospecting having frequently been assessed on a purely empirical basis. During the past 4 years, extensive biogeochemical studies have been carried out in New Zealand (Brooks & Lyon 1966; Lyon et al. 1968; Nicolas & Brooks 1969; Whitehead & Brooks 1969). This research has involved subsequent investigations into the plant chemistry of the species concerned (Lyon, Peterson & Brooks 1969; Lyon, Brooks & Peterson 1969) in order to understand more fully the factors involved in mineral accumulation and metabolism upon which this type of prospecting is based. During recent investigations involving several plant species, it was found that the essential elements copper and zinc showed a relative accumulation distribution different from that for the non-essential elements. The present paper discusses these findings in relation to the suitability of the species concerned for biogeochemical prospecting.