An additive manufacturing apparatus which includes a build platform which is configured to be displaced along a vertical or Z-axis of the additive manufacturing apparatus and a build platform guiding arrangement including: mounting means positioned at or near an extremity of the build platform in a horizontal or X-Y plane defined by an X-axis and a Y-axis of the additive manufacturing apparatus, wherein the build platform is generally rectangular in the X-Y plane and wherein the mounting means is a mounting arrangement provided by a pillar and bush arrangement or pillar and bearing arrangement by which the build platform is mounted in the additive manufacturing apparatus, the mounting means being mounted at a first corner region and being configured operatively to permit displacement of the build platform along the Z-axis and prevent substantial linear displacement of the build platform along the X-axis and/or the Y-axis relative to the mounting means; and guiding means comprising at least two guiding elements , each guiding element including or being provided by a linear guide which extends along the Z-axis and which substantially abuts a side surface of the build platform , the linear guides being fixedly mounted in the additive manufacturing apparatus, the guiding means including a first linear guide mounted at a second corner region on a side of the build platform adjacent to the first corner region, and a second linear guide mounted at a third corner region on another side of the build platform adjacent to the first corner region thereby to permit unconstrained thermal expansion and contraction of the build platform in the X-Y plane and prevent, in use, substantial angular displacement of the build platform about the Z-axis in the X-Y plane. mounting means positioned at or near an extremity of the build platform in a horizontal or X-Y plane defined by an X-axis and a Y-axis of the additive manufacturing apparatus, wherein the build platform is generally rectangular in the X-Y plane and wherein the mounting means is a mounting arrangement provided by a pillar and bush arrangement or pillar and bearing arrangement by which the build platform is mounted in the additive manufacturing apparatus, the mounting means being mounted at a first corner region and being configured operatively to permit displacement of the build platform along the Z-axis and prevent substantial linear displacement of the build platform along the X-axis and/or the Y-axis relative to the mounting means; and guiding means comprising at least two guiding elements , each guiding element including or being provided by a linear guide which extends along the Z-axis and which substantially abuts a side surface of the build platform , the linear guides being fixedly mounted in the additive manufacturing apparatus, the guiding means including a first linear guide mounted at a second corner region on a side of the build platform adjacent to the first corner region, and a second linear guide mounted at a third corner region on another side of the build platform adjacent to the first corner region thereby to permit unconstrained thermal expansion and contraction of the build platform in the X-Y plane and prevent, in use, substantial angular displacement of the build platform about the Z-axis in the X-Y plane. <EOS>