The aggregation behavior of gel microspheres of it-poly(methyl methacrylate) (it-PMMA) from xylene solution was studied using optical microscopy, electron microscopy, DSC and wide-angle X-ray diffractometry. When the dilute solution (0.05-2.0 wt%) of it-PMMA (M-a = 64 000, triad tacticity, 92% isotactic) was cooled to 25 degrees C, the it-PMMA precipitated as swollen, crystalline gel-microspheres (G-MSs) with a diameter of about 1 mu m, which stick together to form complex dendritic clusters, it has been found that the resulting clusters are well described as fractals. The fractal dimension of the aggregates is estimated to be about 1.5. On the other hand, when the rather concentrated solution (similar to 2.0 wt%) was cooled to 10-15 degrees C, G-MSs aggregate to form the porous, highly swollen gel. The process of aggregation of the G-MSs and the structures of gel of it-PMMA are important technologically and scientifically.