Immigration has increased remarkably in Spain over the past ten years. For theoretical reasons, the question has been raised as to whether this population may possibly be responsible for a rise in the incidence and/or transmission of infectious diseases. However, very few studies have been conducted regarding the diseases among this group which would afford the possibility of ascertaining the importance of this statement. This study is aimed at quantifying the hospital care provided to this population in the city of Valencia. The hospital release records were obtained from the Admissions Departments of the public hospitals in the city of Valencia. A one-year retrospective observational study was conducted throughout the October 1, 2001-September 30, 2002 period. We retrieved 8,444 hospital admissions identifying 1,577 hospital admissions of immigrants. Similar percentages of immigrants recorded with their documentation in proper order (841; 51.16%) and immigrants supposedly undocumented (803; 48.84%) were found. Females (68.3%) were predominant over males (31.7%), and a mean age of under 30 years of age. The most frequent diagnosis on release was "pregnancy, childbirth and post-partum-related complications", totaling 37.7% of all releases, others involving, "injuries and poisoning" (12.9%), "digestive tract diseases" (7.8%) and "respiratory tract diseases" (5.4%), "Infectious and parasitic diseases" totaled 4.4%. The percentage of infectious and infectious-contagious diseases found did not contribute to encouraging the opinions disseminated regarding the importing or re-emergence of diseases from the immigrant groups. The en masse immigration which has taken place requires many adaptations of the Healthcare System to afford the possibility of setting out the health profile for this group based on population estimates.