Preliminary studies have been carried out on some nickel-accumulating plants from New Caledonia: Hybanthus austrocaledonicus forms A and B, Hybanthus caledonicus var. linearifolia, and Psychotria douarrei. The Australian nickel accumulator Hybanthus floribundus was also studied for comparison purposes. The nickel content of all the New Caledonian species was extremely high, and reached nearly 16.0% (mass of ash basis) in H. caledonicus var. linearifolia. Except for H. floribundus (29%), most of the nickel in the plants was soluble in water, and reached 94% for P. douarrei (dry mass basis). Column chromatography with Sephadex G-10 gel showed that nickel existed in most species in two forms: a charged complex (molecular mass < 200) and free nickel ions. Ultracentrifugation experiments and electron microprobe studies showed no evidence for the accumulation of nickel in any specific plant tissues. High-voltage electrophoresis paper was used to study amino acid patterns and revealed that the nickel was entirely present in a double-charged form (free and complexed) and was not associated with any of the amino acids. The amino acid patterns, together with data on the morphology, elemental content, and ecology of the plants, indicated that H. caledonicus form B may be a separate variety of the species.