The MALVA (MAntova LongeVA) study aims at investigating the socio-demographic, clinical and genetic characteristics of all subjects over 98 years of age residing in the province of Mantova (Northern Italy). In this paper we present the study protocol and the main demographic results. Absolute number, prevalence ratio and female/male ratio of the subjects aged 98+ and of the centenarians in the Mantova province (370,645 inhabitants at 31st December 1997) were checked at the baseline of the study (31st March 1998) as well as in the two years preceding and following the study. A total of 117 subjects aged 98+ (including 39 centenarians) were traced at 31st March 1998; the prevalence ratio was 31.6 per 100000 (12.1 for centenarians), and the female/male ratio was 6.3 (6.5 for centenarians). The distribution of the oldest old according to places of birth and residence was non-homogeneous across the provincial territory. Seventy-seven subjects (66% of the identified subjects) were enrolled in the study and administered a protocol including an interview about socio-economic conditions, lifetime habits and pathological and pharmacological case histories, as well as medical examination, performance-based tests and blood sample collection. Data on the socio-demographic characteristics and the health status of very old people in the province of Mantova are discussed and compared to findings from previous studies on Italian centenarians.