A few things for optimization purposes... 1. Depth-of-Field - With Bryce's current optimization techniques, the Premium DOF settings are useless. Try the same scene WITHOUT DOF on and you'll see a dramatic, nearly real-time in comparison difference. Nobody in their right mind would ever use Bryce 5.01's DOF setting for animation. Postworking it in After-Effects would take you minutes instead of hours... For stills, nearly any image editor will let you use the "distance mask" option from Bryce to create a more realistic DOF, at a mere fraction of the time... 2. Lighting - I can't see anything in your scene that requires a volumetric lighting setup. No sun-rays, at least not at this point in your render. Turn the volumetrics off if you're not using them... If you're doing volumetric lighting, you should only have one single volume light in the scene. Any other lights will interfere and cast their gels and colors onto the volumetric rays, even if you don't have any gels applied. It's part of Bryce 5's light-gel-bug. 3. Materials - If you really NEED to use volumetrics on this scene, go into the Light Lab for your light. Set volume to "On" before you go into the Gel (Material Lab) setting, as every time you turn Volume Visible to "Off" it will reset your gel material. Brycean volumetric lighting is ALL gel-based, so once into your volume light's Material Lab, you can adjust the volumtric "Quality/Speed" setting to optimize your render. It really never needs to be over 50, I've got a demo of the differences if you're uncertain about it. And if you're test-rendering, and aren't worried about artifacts for the moment, set it to 15 and save yourself some time... 4. Objects - It appears as if you're using many non-Bryce-native objects. Are they imported? Did you model them? Either way, you can cut down on memory and processor load by reducing their polygon counts in a modeler or in a program like PolyTrans. I'm certain there are free programs around that will help you with this, I mostly just stick to PolyTrans and Rhinoceros, which are certainly not free, but very powerful. Remember that Bryce can do some internal smoothing, and so you don't always need those extra polygons at all. Hope some of this blabbering helps you, good luck! (another note on volume lighting - unless the quality is up very high, Brycean volumetrics will not respond well to alpha-based transparencies...)