1. Description of Microforms

2. IDENTIFICATION OF THE KIND OF MICROFORM
Microforms usually fall into one of these kinds:
microfilm
microfiche
microopaque (also known as microprint) (less common)

3. Microforms
The Library of Congress follows Anglo-American Cataloguing Rules, first edition (AACR1) for descriptions of electronic, microform and "on demand" photocopy reproductions of previously existing materials. The principles of AACR1, described in LCRIs for AACR2, chapter 11, state that you should base the bibliographic description on the original publication and place data relating to the reproduction in a secondary position.

4. Microforms
The treatment of an item that is published as a microform edition differs from that of a microform issued as a reproduction of previously published material. 
Items that are microform publications of materials prepared or assembled specifically for bringing out an original edition in microform are cataloged according to chapter 11 of AACR2r.
Items that are microform reproductions of previously published materials, including microform copies of dissertations, are cataloged according to chapter 11 of LCRI. 
Bibliographic information on a record for a microform reproduction must reflect the original publication in these areas: fixed field (except the Form element), title, statement of responsibility, edition, publication information, physical description, and series.  

5. Chief source Chief source: Title frame or title card
When a title card is lacking, eye-readable information on the top of cards may be used
If a title appears in abbreviated form on the microform while the full title appears on the container or is available in accompanying materials, the container or accompanying materials may be used as the chief source

6. 245 Title Statement 
Use subfield h with the appropriate GMD, [microform], immediately following the subfield a:
$a Ecce homo $h [microform] : $b how one becomes what one is / $c Friedrich Nietzsche. 

7. 260 Publication, Distribution, Etc.
When a microform is a reproduction of previously published material, the information in this field should reflect that of the original edition.  The 533 field will contain the details of the publication of the reproduced material

8. 300 Physical Description 
When the microform is an edition issued in microform, code the 300 to represent the item in hand.  For a microform that is a reproduction of previously published material, code the 300 to the original edition. 
Microform edition: 
300     $a 2 microfilm reels : $b ill. ; $c 35 mm.
Previously published material now issued in microform:  
300     $a 756 p. : $b ill. ; $c 28 cm. 

9. 533 Reproduction Note 
This field is mandatory when cataloging a microform that is issued as a reproduction of previously published material.  Do not use the 533 field when cataloging an edition issued in microform. 
subfield a=type of reproduction
subfield b=place of reproduction
subfield c=agency responsible for reproduction
subfield d=date of reproduction
subfield e=physical description of reproduction
subfield f=series statement of reproduction (if applicable) 

10. 533 Reproduction Note 
533     $a Microfilm. $b Ann Arbor, Mich. : $c UMI Reprints on Demand, $d $e 2 microfilm reels ; 35 mm.  
533     $a Microfiche. $b Needham, Mass. : $c Omnisys, $d $e 2 microfiches. $f (French Revolutionary pamphlets on microfiche ; no. 8856) 

11. Fixed Field and 007 Fixed Field: Form a (microfilm) b (microfiche)
 c (microopaque
007 Physical Description Fixed Field (R)
 $a h $b d /or e $d a / or b $e f / or m ... $f a--- /or b--- etc. $g b / or c or m $ h a / or b... $ i a / or b... $j a / or u...
$b: d (for microfilm); e (for microfiche)
$d: a (positive); b (negative)
$f: Reduction ratio: use four character positions (see Bib. Standard and Format for details)
$g: b (monochrome); c (color); m (combination of color and monochrome)...
$h: a (silver halide); b (diazole); c (Vesicular)...
$i:  a (first generation master); b (printing master); c (Service copy)...
$j:  a (safety base); u (unknown)...

12. Guides
Microform that is issued with an accompanying guide should be cataloged on the same bibliographic record.  If a guide is published at a later date, has a different title and is not issued by the same body, catalog it on a separate bibliographic record. 
300     $a 8 microform reels ; $c 35 mm. + $e guide (xiv, 56 p. : ill. ; 28 cm.) 
500 $a Accompanied by a printed guide, entitled: Guide to records of the U.S. Department of State relating to internal affairs of Czechoslovakia,  

13. Linking
LC links bibliographic records for microform reproductions of monographs to records for the corresponding hardcopy originals.
LC adds field 776 to records representing microform reproductions. Field 776 consists of subfield ‡c with "Original" and subfield ‡w with the National Union Catalog symbol in parentheses followed by the control number of the record for the hardcopy original.
7761‡c Original ‡w (DLC)   
The preceding example shows a link for a microform reproduction of The Toll of the Sands, LCCN Do not use a similar linking field on the record for the hardcopy original to connect it with its microform reproductions.