Comic Title: Superman #227
Publisher: DC (National Periodical Publications, Inc.)
Address: 909 Third Avenue, New York, NY
Cover Date: Jun/Jul 1970
On Sale Date: April 14, 1970 Newsstand Date April 14, 1970
Source: House Ad, Flash #197, Page 10

Copyright Date April 14, 1970
Source: Library of Congress, Periodicals 1970

Frequency: Monthly, with the exception of March and September
Cover Price: $0.25
Page Count: 64
Editor: Mort Weisinger

See Also: The Guide to DC Giants

Notes:
This issue is numbered Giant #G72.

Title: "The Great Kryptonite Mystery"
Pages: 8

Feature(s):
Superboy (of Earth-1)

Writer: Jerry Coleman
Penciller: Curt Swan
Inker: Ray Burnley

Reprinted From:
Superboy #58 (1957)

Feature Character(s)

• Superboy (last appearance in Superboy #58; next appearance in Showcase #9)

Supporting Character(s)

• Jonathan Kent (last appearance in Superboy #58; next appearance in Adventure Comics #238)
• Martha Kent (last appearance in Superboy #58; next appearance in Adventure Comics #238)

Villain(s)

• Ten Kryptonian criminals (no appearance)

Other Character(s)

• Various military personnel (no further appearances)

Comments:
Superboy learns that ten Kryptonian criminals were exiled in a space satellite due to arrive on Earth in 15 years. These criminals must have been exiled before the discovery of the Phantom Zone.

Synopsis:
Superboy begins deliberately exposing himself to Kryptonite meteors and collecting them in a secure vault. He refuses to tell anyone why he is hurting himself. The continued exposure causes the Boy of Steel to become ill and his powers weaken. After collecting several such meteors, Superboy hides the vault of Kryptonite on the ocean floor. He explains to his foster parents that he hoped to build up an immunity to the Kryptonite meteors, so that he could use them later against ten Kryptonian criminals due to arrive on Earth in 15 years.