Additions to the adventitious flora of the Netherlands, mainly found in 1966. 1. Osmunda claytoniana L., a native of the eastern part of N. America, has established itself in the park ‘Het Loo’, near Apeldoorn (prov. Gelderland). 2. Polygonum cilinode Michx., also of N. American origin, was found in large quantities near Wageningen (prov. Gelderland). 3. Brassica juncea Czern. var. sabellica (Pleck) Kitamura, a form with laciniate, crispate leaves, occurred as a ruderal at Beverwijk (prov. N. Holland). 4. Heliophila longifolia DC., a native of South Africa, was found near an oil-factory at Zaandijk and on a railway-yard at Zaandam, both in the prov. of N. Holland. 5. The Central and E. European Sisymbrium strictissimum L. was found along a roadside near Leiden. 6. Seedlings of Ceratonia siliqua L. occurred on a railway-yard in the harbour of Rotterdam and along the river Zaan in the province of N. Holland. 7. Ononis alopecuroides L., a native of the Mediterranean region, was found in the harbour of Rotterdam. 8. In the same locality seedlings of Citrus spec, were found. 9. Bupleurum croceum Fenzl, a native of SW. Asia, was found at Leiden. 10. Moluccella laevis L., probably introduced with materials for dry bouquets, was found on a rubbish dump near Beverwijk (prov. N. Holland) and occurred spontaneously in gardens at Beilen (prov. Drente) and Midwolde (prov. Groningen). The species is native in the eastern part of the Mediterranean region. 11. Scutellaria altissima L., a native of the eastern part of the Mediterranean region, was found along a roadside between Beverwijk and Wijk aan Zee (prov. N. Holland). 12. Sideritis hyssopifolia L. occurred near a factory for cattle fodder at Oost-Knollendam (prov. N. Holland); it is a native of SW. Europe. 13. Plantago ovata Forsk., known from the Mediterranean region and eastwards as far as N. India, was found near Itteren (prov. Limburg), along the river Meuse, and in the harbour of Rotterdam. 14. Under this number five species are enumerated; these are escapes from cultivation.