Five different cultivars of Thymus vulgaris originating from various geographical sources (Canada, F.R. Germany, former GDR, and Spain) were first propagated by cuttings from each cultivar in the greenhouse and then cultivated organically in the fields during the periods of 1993–1995 (Quebec, Canada) and 1996–1997 (Washington State). The field-grown plants were harvested in mid-September. The oils obtained through steam distillation of the dried leaves from each cultivar were analyzed by means of TLC followed by GC. The oil content varied from 1.38% to 2.04% in Quebec, and 1.41% to 2.25%, depending on the cultivar used. The highest oil content was obtained from `Madrid', followed by `RH-1' and `Laval-1'. More than 95% of the oil, with a total of 24 components, were identified in the samples. `Laval-1', recently developed in Quebec, `Madrid' from Spain, and `RH-1' from Germany were established to belong to thymol-chemotypes, while `RH-2' from Germany was found to be carvacrol-chemotype. `QDLB', from the former GDR, was characterized by its ≈39% thymol, 17% carvacrol, and 3.52% linalool content in the oil. The content of thymol and its ratio was found to change slightly with shifting cultivation of the cultivars from Europe to North America. Other important constituents in the essential oils were also p-cymene (10.87–22.89%), g-terpinene (2.21–8.85%), α-pinene (0.87–2.23%), sabinene (0.00–1.77%), borneol (0.00–3.69%), geraniol (0.59–3.48%), and terpinen-4-ol (0.21–3.08%). As `Laval-1' and `RH-1' showed better overwintering ability and produced relatively higher leaf yields. These two cultivars were found to be prospective cultivars for commercial organic cultivation for North America. Results obtained from various growing areas are presented.