The objective of this study was to determine changes in the level of anthocyanins, polyphenols, and antioxidant activity of strawberry jams stored at a temperature of 4°C. The antioxidant activity of freshly manufactured strawberry jams amounted to 31.2 mg per 100 g of fresh product. The pelargonidyne-3glucosid was a dominant monomer, its per cent content was 92.5% of the total anthocyanin content, the cyanidyno-3-glucosid per cent content was 4.4%, and the pelargonidyne-3-arabinosid: 3.1%. It was stated that the content of anthocyanins in strawberry jams after their having being stored for 30 days was by 1.2 times lower if compared with the initial samples, and 1.6 times lower after the 60 day storage. Furthermore, the investigation showed that changes in the contents of biologically active components of low-sweetened jams in storage varied. The antioxidant activity was proved to be the resultant effect of content levels of many components, including anthocyanin dyes, and of the total amount of all the polyphenol compounds. A long-time storage of products under investigations appeared to be unfavourable because of the instability of anthocyanins, in particular the pelargonidyne. When jams were stored during a period of 60 days, the degradation index of the components analyzed increased from 1.4 to 1.7. The degradation rate and the decrease in antioxidant potential of jams showed a more intense profile during a 60-day storage period.