When he was unable to find work in Spain, Josep Toutain (1930-1997) moved to France. He secured more than he could undertake and organised colleagues Rafael López Espí, Francisco Cueto and José María Miralles to assist. During the company's first stage, most of the foreign orders came from Toutain's French contacts.

In 1954, he established a studio in an attic on the corner of Paseo de Gracia and Calle Mallorca in Barcelona, initially in association with publisher Antonio Ayné Arnau, co-owner of Toray. In 1956 the company was formally established and relocated to a new studio on Provenza street, between Cartagena and Dos de Mayo.

From the mid 1950s, Toutain and Jordi Macabich (founder of Bardon Art), traveled by motorcycle to London and established contacts with the British comic industry. From the late 1950s to the 1970s, Fleetway comics were dominated by SI Artists, especially romance but also other genres.

During this period, SI began to work for the Scandinavian and then the German markets, in association with Guillermo Hierro. The German work helped the agency transition to providing full colour and painted art. The agency expanded internationally, with direct orders or syndicated work supplied to Great Britain, Denmark, Norway, Sweden, Finland, Germany, France, Italy, Portugal, Yugoslavia, Turkey, Argentina, Brazil, Mexico, Japan, Australia and India.

SI also produced many photo-comics, especially for France and Italy, with the company's artists acting as extras.

From 1971 to 1983, SI work dominated US Warren magazines, began with Vampirella #11 in May 1971. SI artists also contributed to US Skywald in the early to mid-1970s. Many of these stories were later published in Spanish magazines.

In 1973, Toutain created Toutain-Editor and focused his attention on publishing and by the 1980s the agency was in decline. Some leading artists left the agency and Warren went bankrupt in 1983. Toutain created a US publisher, Catalan Communications.

SI subsequently licensed US characters, including from Disney. After the death of Toutain in 1997, it moved solely into illustration and continues to operate as at 357 Balmes Street, Barcelona.

Los profesionales by Carlos Giménez is a fictionalized account on his time at the SI studios, which is titled Creaciones Ilustradas in the comic. Fernando Fernández wrote a memoir, Memorias Ilustradas, about his time at the agency.