Objectives: To assess the impact of the COVID-19 pandemic on the activity of clinical laboratories in Spain.Methods: A descriptive, observational, retrospective, multicenter study.Results: Between March and December 2020, there was a statistically significant decrease in the number of test requests (-17.7%, p=< 0.001) and total tests performed (-18.3%, p < 0.001) with respect to the same period in 2019. A decrease was observed in the number of requests from primary care (-37.4%) (p < 0.001) and in the number of foecal occult blood (-45.8%); qualitative urine (-30.1%); PSA (-28.5%); TSH (-27.8%); total cholesterol (-27.2%) and HbA(1c) (-24.7%) tests performed, p < 0.001. A significant increase was found in the number of requests from ICUs (76.6%, p < 0.001) and number of IL-6 (+22,350.9), D-dimer (+617.2%), troponin (+46.8%) and arterial blood gas (+3.9%) tests carried out, p < 0.001. During the first months of 2021, there were significant changes in the number of requests for qualitative urine (-8.7%, p < 0.001), PSA (-6.3%, p=0.009), IL-6 (+66,269.2, p < 0.001), D-dimer (+603.6%, p < 0.001), troponin (+28.7%, p < 0.001), arterial blood gas (+26,2%, p=0.014) and ferritin (+16.0%, p=0.002) tests performed.Conclusions: There were changes in the origin and number of test requested to clinical laboratories in Spain. The number of requests for the evaluation and monitoring of COVID-19 patients increased, whereas requests for the control of non-COVID patients and for population screening decreased. Long-term analysis reveals that the volume of tests performed for the control of chronic diseases returned to normal over time, whereas the increase observed in the volume of tests performed for the management of COVID-19 patients is maintained.