Theo van Rysselberghe came from a family of architects. He began studying art in Ghent and then in Brussels. His first paintings were definitely classical in style, but later he overcame his resistance to Neo-Impressionist theories, and at the last Impressionist exhibition in 1886 he broke his walking stick in front of Seurat's picture La Grand Jatte. However two years earlier he had been involved in starting an avant-garde group in Brussels, known as Les Vingt, and he was also their Paris correspondent. This group had no special theories; its only object was to get up exhibitions illustrating the newest tendencies in European art. In 1888, the Vingt group invited Signac, Dubois-Pillet and Cross to come and visit them, and as a result several Belgian painters, Rysselberghe among them reached a very much better understanding of Neo-Impressionism. Not long after that Rysselberghe, who had become friendly with Seurat, Signac and Cross, began to practice divisionism in his portrait painting using small dots of different sizes on one canvas. He went on practicing this divisionist technique until about 1910, although towards the end of his life he reverted to a more academic style.  He exhibited not only with the Vingt but also with the  Libre Esthetique, Art Contemporain and Independants, and also sometimes at the official Paris Salon. Rysselberghe was involved with various artistic groups and was a close friend of Verhaeren, whose portrait he painted in 1913. Rysselberghe often went abroad, particularly to Morocco, before finally settling in Paris in 1898. He had a great influence on the development of' Neo-Impressionism in Belgium, more perhaps through his connection with the Group des Vingt than by his actual painting.  A retrospective exhibition of his works  was held in 1927 in Brussels, a year after his death; Maurice Denis wrote the introduction to the catalogue.

Based on Phaidon encyclopedia of Impressionism, Maurice Serullaz, Phaidon, 1978