Euonymus europaeus seeds and seed oil were investigated for their volatiles using GC-MS-FID and Headspace- SPME/GC-MS-FID, and for their non-volatile compounds using derivative GC-MS-FID and HPLC-DADCAD/ MS. The seeds contain about 30% of fatty oil, mainly glyceryl trioleate, small amounts of abietadiene and -triene, dihydroagarofurane sesquiterpenes, and alkaloids of the sesquiterpene pyridine type. Breakdown products of the latter can be found by transesterification with tetramethylammonium hydroxide. In the seed oil, glyceryl acetates are slowly formed through cleavage of alkaloids and triglycerides. Bioassay results indicated both the seed oil and methanol extract had weak repellent and larvicidal activity against the yellow fever mosquito (Aedes aegypti), and were ineffective in repelling the long star tick (Amblyomma americanum) at the concentrations tested.