In response to public concerns regarding the health impact of nuclear submarines stationed at Île Longue, changes in the incidence of childhood cancers around the Brest harbor have been described. Using data collected by the Breton Childhood Cancer Registry, leukemias were distinguished from all other cancers. Finistère was divided into three zones: (i) Finistère excluding the Brest harbor, (ii) the Brest harbor excluding Brest, (iii) Brest. The study period, spanning 1991 to 2005, was analyzed either continuously or by period depending on the size of the zone. Analyses were performed using external reference with indirect standardization by age on the one hand, and internal reference on the other. An excess incidence of leukemia was observed across the entire Finistère region, due to an excess in 2000–2001 in Brest. The description of all cases occurring in Brest during the 2000–2005 period did not provide evidence supporting a cause linked to occupational exposure of parents in defense nuclear activities. An increase in the incidence of all cancers except leukemias was observed in Finistère between 1999 and 2004. No increase was observed either in the Brest harbor or in Brest. The 2005 incidence is closer to the national incidence. The isolated peak in incidence observed in Brest in 2000–2001 does not appear to support a persistent environmental cause but should be monitored in the future. It seems important to verify a return to normal levels of incidence for all cancers except leukemias for the years following 2005 in the Finistère department. (R.A.)