Countercharm
To Kill or Cure
Red Alert
Tableau
The Conspirators
The Scavengers

These originally appeared between 1953 and 1960 - most from New Worlds, and one from Astounding. The first story is in his "Sector General" series, the others are good reading - I recommend this, as well as most books by James White.

This British reprint is the only hardcover edition, and rather scarce. It contains 6 of 7 stories from the 1969 American paperback, omitting "Occupation: Warrior."