The Mexican International Conference on Arti?cial Intelligence (MICAI) is aimedatpromotingresearchinarti?cialintelligence(AI)andcooperationamong Mexicanresearchersandtheirpeersworldwide. MICAIisorganizedbytheMe- canSocietyforArti?cialIntelligence (SMIA) incollaborationwiththe American Association for Arti?cial Intelligence (AAAI). After the success of the three previous biannual conferences, we are pleased to announce that MICAI conferences are now annual, and we present the p- ceedings of the 4th Mexican International Conference on Arti?cial Intelligence, MICAI 2005,held onNovember14-18,2005,inMonterrey,Mexico. This volume containsthe papersincludedinthemainconferenceprogram,whichwascomp- mentedby tutorials,workshops,andpostersessions,publishedinsupplementary proceedings. The proceedings of past MICAI conferences were also published in Springer'sLectureNotesinArti?cialIntelligence(LNAI)series,vols. 1793,2313, and 2972. Table1. Statistics of submissions and accepted papers by country/region 1 1 Authors Papers Authors Papers Country/Region Subm Accp Subm Accp Country/Region Subm Accp Subm Accp Algeria 2 - 0. 66 - Lithuania 3 1 1. 5 0. 50 Argentina 27 4 8. 66 1. 5 Malaysia 2 - 1 - Australia 7 - 2. 66 - Mexico 383 139 131. 91 47. 44 Brazil 48 14 15. 16 3. 66 Netherlands 3 2 1. 2 1 Bulgaria 1 1 0. 5 0. 5 New Zealand 4 4 1 1 Canada 13 4 4. 75 2 Norway 4 1 2. 33 1 Chile 14 10 6 4 Poland 8 2 3 1 China 288 65 107. 33 23. 66 Portugal 2 - 0. 5 - Colombia 1 - 1 - Romania 2 2 0. 5 0. 5 Cuba 6 - 1. 66 - Russia 10 3 7 1.