1-Ethers may be cracked over untreated .gamma.-alumina having a pore volume of more than 1.0 cc/g and an average pore diameter of more than 150 angstroms (.ANG.) at a temperature from 250 to 350.degree. C. and a pressure from 10 to 200 kPa at high conversions and good selectivity to produce the corresponding 1-alkene. The process is particularly useful to produce 1-octene from 1-methoxyoctane.