Best Science Fiction Stories of the Year: Best science fiction of the year ; fourth annual collection by Lester del Rey

A Little Knowledge / Poul Anderson
Autumntime / A. Lentini
Foreword: Alternate Possibilities / Lester del Rey
Good News from the Vatican / Robert Silverberg
Hot Potato / Burt K. Filer
I’ll Be Waiting for You When the Swimming Pool Is Empty / James Tiptree Jr.
Occam’s Scalpel / Theodore Sturgeon
Ornithanthropus / B. Alan Burhoe
Rammer / Larry Niven
The Human Operators / Harlan Ellison and A.E. van Vogt
The Man Underneath / R.A. Lafferty
The Power of the Sentence / David M. Locke
The Science Fiction Yearbook (1971) / essay by Lester del Rey
The Sliced-Crosswise Only-On-Tuesday World / Philip José Farmer
The Wicked Flee / Harry Harrison
To Make a New Neanderthal / W. Macfarlane, as Wallace Macfarlane
When You Hear the Tone / Thomas N. Scortia