Abstract Forty compounds have been characterized by GC and GC/MS and relative retention times in 300 samples of Niaouli (Melaleuca quinquenervia) oils collected on 75 different trees during four seasons. Twenty-one compounds were submitted to multivariate statistical analyses using Principal Component Analysis (PCA). Factorial Discriminant Analysis (FDA) revealed the presence of three chemotypes. Chemotype I is already known (1,8-cineole; 50%), chemo-type II had an equal content in 1,8-cineole (33%) and viridiflorol (32%). The third (chemotype III) was characterized by a high content in viridiflorol (50%). The 1,8-cineole chemotype represented 58% of three populations. Seasonal differentiation does not occur, showing that Niaouli oil composition is stable all year.