4Pi-confocal microscopy provides three-dimensional images of the microtubule network with 100- to 150-nm resolution.

We show the applicability of 4Pi-confocal microscopy to three-dimensional imaging of the microtubule network in a fixed mouse fibroblast cell. Comparison with two-photon confocal resolution reveals a fourfold better axial resolution in the 4Pi-confocal case. By combining 4Pi-confocal microscopy with Richardson-Lucy image restoration a further resolution increase is achieved. Featuring a three-dimensional resolution in the range 100-150 nm, the 4Pi-confocal (restored) images are intrinsically more detailed than their confocal counterparts. Our images constitute what to our knowledge are the best-resolved three-dimensional images of entangled cellular microtubules obtained with light to date. Copyright 1998 Academic Press.