This study assesses seroprevalence of SARS-CoV-2 in Spain from a sample of 61,075 participants from 35,883 randomly selected households. Using a point-of-care test and an immunoassay, the authors calculated seroprevalence as 5% and 4.6% respectively, with specificity-sensitivity in the range of 3.7-6.2%. No significant difference is reported by sex, though significant differences are observed by geography (>10% in Madrid compared to <3% in coastal regions), and by age (seroprevalence in children under 10 was <3.1%). 21.9-35.8% of seropositive individuals were asymptomatic based on self-report questionnaires. Among individuals with anosmia or at least 3 symptoms, seroprevalence was between 15.3-19.3%; only about 19.5% of symptomatic individuals who were seropositive by both tests reported a previous PCR test. The study suggests the majority of PCR-confirmed cases had detectable antibodies, but there is a high proportion of asymptomatic individuals, as well as symptomatic individuals not previously tested.