This study was designed to ascertain the organisational practices of learning support teachers and their perceptions of the benefits, if any, of support by withdrawal for mathematics in Irish primary schools. The study reports on the views of a sample of 137 teachers who have postgraduate qualifications in learning support/special education from six designated centres for professional development in this area. As an organisational model for learning support in mathematics, small group/individual withdrawal was the most popular way in which additional support was organised, with 94% of the survey respondents in this study operating this system to some degree. Furthermore, key findings also highlighted that teachers perceived the following as advantages to out-of-class support: learning benefits; enhanced learning space; benefits for certain types of pupils; time benefits; positive contrast with mainstream class; assessment benefits; and greater use of concrete materials. In contrast, only 41% of teachers reported that they provide an in-class service for pupils and class teachers. Barriers to collaboration for in-class support are identified and teachers' responses to these outlined. The study found large differences between teachers in the amount of support they provided to class teachers, the amount of non-contact time they had for planning and collaboration, and in the range of practices used to carve out time for collaboration. The implications of these findings are then discussed. (Contains 5 tables and 1 figure.)