The crystallization from dilute solution of two long n-alkanes (C246H494 and C162H326) has been followed in real time using synchrotron X-ray diffraction techniques at the European Synchrotron Radiation Source (ESRF) at Grenoble. The data confirm the existence of minima in crystallization and nucleation rates in C294H590. Further, the ability to record data very rapidly has allowed us to see the minimum in crystallization rate in C162H326 for the first time. Small changes in lattice spacing were seen during and after crystallization in all samples. These indicate that there is some perfectioning of crystals-for example the removal of cilia at the surfaces, etc. (C) 2003 Elsevier Science Ltd. All rights reserved.