Two-stage　data　envelopment　analysis　(DEA)　has　been　researched　by　a　number　of　authors.　In　a　recent　paper　by　Kao　and　Hwang　(2008),　the　overall　efficiency　of　two-stage　process　was　defined　as　the　product　of　the　efficiencies　of　two　individual　stages.　In　a　more　recent　paper　by　Chen,　Cook,　Li,　and　Zhu　(2009),　the　overall　efficiency　of　two-stage　process　was　modeled　as　a　weighted　sum　of　the　efficiencies　of　two　individual　stages.　This　paper　looks　into　further　two-stage　DEA　and　proposes　some　alternative　DEA　models　for　two-stage　process　to　show　that　(i)　the　overall　efficiency　of　two-stage　process　can　also　be　modeled　as　a　weighted　harmonic　mean　of　the　efficiencies　of　two　individual　stages:　(ii)　the　two-stage　DEA　model　of　Kao　and　Hwang　(2008)　can　be　easily　extended　to　variable　returns　to　scale　(VRS)　assumption;　and　(iii)　the　additive　efficiency　decomposition　model　of　Chen　et　al.　(2009)　can　be　generalized　to　taking　into　account　the　relative　importance　weights　of　two　individual　stages.　Numerical　illustrations　are　provided　to　show　the　potential　applications　of　the　proposed　new　DEA　models.　(C)　2010　Elsevier　Ltd.　All　rights　reserved.