Republican candidate Mark Hatfield was re-elected to a fifth term, defeating Democratic businessman Harry Lonsdale.

For the Democrats, Harry Lonsdale, who had founded the biotechnology company Bend Research, announced in early 1990 that he intended to aggressively challenge Hatfield over the incumbent's ties to special interests, and his positions on abortion rights and timber management.

[1] In the Republican primary, Hatfield received a token challenge from Randy Prince, an environmentalist and former Eugene mayoral candidate who had once protested old-growth forest logging by tree sitting for 40 days.

[4] Lonsdale, who was unknown as a politician, announced his campaign in March, and came out swinging directly at Hatfield and mostly ignored his primary challengers.

[1] Lonsdale easily defeated his competition: Salem attorney Steve Anderson, Pleasant Hill computer programmer Neale S. Hyatt, Milwaukie retired truck driver Brooks Washburne, Eugene activist Bob Reuschlein, and Frank A. Clough, also of Eugene.

[4] Lonsdale's self-financed campaign made heavy use of TV attack ads, criticizing Hatfield as being out of step with Oregonians on every issue, but primarily in terms of timber and abortion.