The Secret Agent; a Simple Tale
in Ridgway's (New York, NY, USA) (Oct 6, 1906 — Dec 15, 1906):
Vol. 1, No. 1 (Oct 6, 1906): 
pp.0–67
Vol. 1, No. 2 (Oct 13, 1906): pp.1–67
Vol. 1, No. 3 (Oct 20, 1906): pp.0–67
Vol. 1, No. 4 (Oct 27, 1906): pp.1–67
Vol. 1, No. 5 (Nov 3, 1906): pp.1–67
Vol. 1, No. 6 (Nov 10, 1906): pp.0–67
Vol. 1, No. 7 (Nov 17, 1906): pp.0–67
Vol. 1, No. 8 (Nov 24, 1906): pp.0–51
Vol. 1, No. 9 (Dec 1, 1906): pp.0–51
Vol. 1, No. 10 (Dec 8, 1906): pp.0–51
Vol. 1, No. 11 (Dec 15, 1906): pp.0–51
pp.0–67 Vol. 1, No. 2 (Oct 13, 1906):
pp.1–67 Vol. 1, No. 3 (Oct 20, 1906):
pp.0–67 Vol. 1, No. 4 (Oct 27, 1906):
pp.1–67 Vol. 1, No. 5 (Nov 3, 1906):
pp.1–67 Vol. 1, No. 6 (Nov 10, 1906):
pp.0–67 Vol. 1, No. 7 (Nov 17, 1906):
pp.0–67 Vol. 1, No. 8 (Nov 24, 1906):
pp.0–51 Vol. 1, No. 9 (Dec 1, 1906):
pp.0–51 Vol. 1, No. 10 (Dec 8, 1906):
pp.0–51 Vol. 1, No. 11 (Dec 15, 1906):
pp.0–51 - Collected as The Secret Agent: A Simple Tale in The Secret Agent: A Simple Tale (1907)
- Subsequently serialized as L'Agent secret: Simple histoire in Le Temps (Paris, France) (May 31, 1910 — Jul 8, 1910)
- Subsequently serialized as The Secret Agent in Classics Illustrated (New York, NY, USA) (Jan 1990)
View in Internet Archive BookReader (experimental). 
Illustrated by Henry Raleigh.
For a detailed discussion of Conrad's The Secret Agent in Ridgway's see Sid Reid's essay in the Scholarship section.
For a detailed discussion of Conrad's The Secret Agent in Ridgway's see Sid Reid's essay in the Scholarship section.