Solanum melongena cotyledon explants grown on hormone-free medium (controls) or on medium containing either naphthalenacetic acid alone (root forming) or in combination with zeatin riboside (shoot forming), showed minor differences in free polyamine titres during culture. In contrast, coniugated polyamines accumulated only in hormone-treated explants, but not in controls. Differences between the two organogenetic programmes with respect to temporal changes in polyamine content, and putrescine biosynthetic and oxydative activities are discussed in relation to the timing of organ formation. The latter was monitored both histologically and microscopically