1966 - 255,070 [Lee/Kirby/Roth, Thomas/Roth] published mothly beginning in September 1963
1967 - 266,034 [Thomas/Roth, Thomas/Andru]
1968 - 273,360 [Thomas/Heck, Freidrich/Heck, Drake/Heck, Drake/Steranko]
1969 - 235,811 [Drake/Heck, Thomas/Adams]
1970 - N/A - cancelled March 1970 (issue #66), revived December 1970 (issue #67) as a bi-monthly reprint title
1971 - 164,169 - bi-monthly reprints
1972 - N/A - bi-monthly reprints
1973 - 127,653 - bi-monthly reprints
1974 - N/A - bi-monthly reprints
1975 - 119,231 [Claremont/Cockrum] resumed August 1975 as a bi-monthly title (issue #94)
1976 - 115,992 [Claremont/Cockrum]
1977 - 123,725 [Claremont/Cockrum]
1978 - 115,260 [Clarement/Byrne] resumed monthly schedule in August 1978 (issue #112)
1979 - 171,651 [Clarement/Byrne]
1980 - 191,927 [Clarement/Byrne]
1981 - 259,007 [Clarement/Cockrum] renamed Uncanny X-Men in February 1981 (#142)
1982 - 373,225 [Clarement/Cockrum]
1983 - 336,824 [Clarement/Smith]
1984 - 378,135 [Claremont/Romita Jr.]
1985 - 448,870 [Claremont/Romita Jr.]
The numbers peaked in 1993 [714,675] with the speculator boom.