Exhibit 11
 
                   CABOT CORPORATION AND CONSOLIDATED SUBSIDIARIES
 
               STATEMENT REGARDING COMPUTATION OF PER SHARE EARNINGS
                 For the three month period ended December 31, 1997
                   (Amounts in millions, except per share amounts)
 


                                                                                                    BASIC      DILUTED
                                                                                                  ---------  -----------
                                                                                                       
 
Shares of common stock outstanding at October 1, 1997, less treasury stock......................       69.5        69.5
 
Plus net weighted shares of treasury stock purchased............................................       (1.0)       (1.0)
 
Less contingently issuable shares...............................................................       (2.4)        --
 
Plus common stock equivalents:
 
  Effect of convertible preferred stock conversion..............................................       --           6.0
 
  Effect of equity incentive awards.............................................................       --           0.8
                                                                                                  ---------       -----
 
Weighted average shares outstanding.............................................................       66.1        75.3
                                                                                                  ---------       -----
                                                                                                  ---------       -----
 
Income applicable to common shares..............................................................  $    30.7   $    30.7
 
Dividends on preferred stock....................................................................       --           0.8
 
Preferred stock conversion compensation shortfall...............................................       --          (0.4)
                                                                                                  ---------       -----
 
Earnings applicable to common shares............................................................  $    30.7   $    31.1
                                                                                                  ---------       -----
                                                                                                  ---------       -----
 
Earnings per common share.......................................................................  $    0.46   $    0.41
                                                                                                  ---------       -----
                                                                                                  ---------       -----