Until 1997 Spain was the European country with the highest incidence of AIDS, due mainly to transmission between users of injected drugs. Since early 1990 there has been a fall in the rate of diagnoses of HIV infection in the Spanish autonomous communities where this information is available, and in 2004 this rate was situated below that of several western European countries. New infections in users of intravenous drugs have declined, and although heterosexual transmission has not undergone significant changes, it has become the prime cause of new HIV infections. The rate of diagnoses of HIV has fallen in both the indigenous population and immigrants; however, demographic changes have meant an increase in the percentage of HIV diagnoses in immigrants. In homosexual men there have been descriptions of a recent increase in the incidence of syphilis and gonococcus, which are a warning of possible increases in the transmission of HIV in this group. The number of people who live with HIV in Spain remains between 100,000 and 150,000 (2.4 to 3.6 per 1,000 inhabitants). In spite of the improvement in prognosis due to antiretroviral treatments, there are annually in Spain over 2,000 cases of AIDS (4.8 per 100,000 inhabitants) and over 1,600 deaths from AIDS (3.8 per 100,000). One third of the people who developed AIDS in 2004 had not until then been diagnosed with HIV, which prevented starting the antiretroviral treatment in time.