<PAGE>
FILED PURSUANT TO RULE 424(b)(3)
REGISTRATION NO.: 333-86257
Supplement, Dated April 12, 2000, to Prospectus, Dated September 17, 1999, of
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UnitedGlobalCom, Inc.
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Additional Selling Securityholders. The following selling securityholders are
added to the list of selling securityholders in the prospectus:
<TABLE>
<CAPTION>
Number of Depositary Shares
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Name of Selling Securityholder Owned Offered
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<S> <C> <C>
Lutheran Brotherhood High Yield Fund 40,000 40,000
LB Series Fund Inc., High Yield Portfolio 60,000 60,000
</TABLE>
