This is happening because the maps data has data that is out of the range of [-180, 180], either from the source data itself or from the clipping somehow: range(world.map$x, na.rm = TRUE)  -179.9572 190.2908 You would have to carefully clean this up to make it useable, but I would just avoid it and use the clean data set in maptools (or import your own from some other source. Here you can intersect a polygon with wrld_simpl to clip it from the infinities at the poles before reprojecting Dear Mike, Thank you for your answer. I get an error with the polygons intersection: Error in RGEOSBinTopoFunc(spgeom1, spgeom2, byid, id, ‘rgeos_intersection’) : TopologyException: side location conflict at -91.437497778887078 17.241108073444931 The problem seems to be a bad polygon in the wrld_simpl database  FALSE Warning message: In RGEOSUnaryPredFunc(spgeom, byid, ‘rgeos_isvalid’) : Ring Self-intersection at or near point -95.902496339999999 66.946641920000005 Any way to fix it? BTW, I You need to provide the version of rgeos you are using – from sessionInfo(), and the messages printed when rgeos is loaded. For me with rgeos: (SVN revision 360) GEOS runtime version: 3.3.5-CAPI-1.7.5 Polygon checking: TRUE and: R version 2.15.2 (2012-10-26) Platform: x86_64-unknown-linux-gnu (64-bit) … other attached packages:  rgeos_0.2-9 rgdal_0.7-22 maptools_0.8-20 lattice_0.20-10  sp_1.0-2 foreign_0.8-51 there is no problem. On the same system, I also see this, but it isn’t the Thank you Roger. Below what I get (didn’t change after update.packages(‘rgeos’)) rgeos: (SVN revision 357) GEOS runtime version: 3.3.3-CAPI-1.7.4 Polygon checking: TRUE R version 2.15.1 (2012-06-22) Platform: x86_64-apple-darwin9.8.0/x86_64 (64-bit) locale:  C attached base packages:  grid stats graphics grDevices utils datasets methods base other attached packages:  rgeos_0.2-8 rgdal_0.7-22 maptools_0.8-18 lattice_0.20-10 sp_1.0-2  foreign_0.8-51 Hope this helps. /Gis Source.