The EFSA Panel on Contaminants in the Food Chain (CONTAM Panel) assessed the risks to human health related to the consumption of spirolides (SPXs), gymnodimines (GYMs), pinnatoxins (PnTXs) and pteriatoxins (PtTXs) in shellfish. They are cyclic imines (CIs), a family of marine biotoxins. SPXs and GYMs are produced by the dinoflagellates Alexandrium ostenfeldii and Karenia selliformis, respectively. The organism producing PnTXs has not been identified but has been described as a peridinoid dinoflagellate. PtTXs are suggested to be bio-transformed from PnTXs in shellfish. No information has been reported linking CIs to poisoning events in humans. SPXs have been detected in Europe while GYMs have not been found. Recently PnTXs were identified for the first time in shellfish in Europe but PtTXs have not been detected. There are no regulatory limits for CIs in shellfish. The toxicological database for SPXs, GYMs, PnTXs and PtTXs is limited, comprising mostly acute toxicity studies. In view of the acute toxicity and the lack of chronic toxicity data for CIs, the CONTAM Panel considered that an acute reference dose should be established but due to the lack of data this was not possible. By comparing the lowest lethal dose (LD50) values for SPXs (50 and 500 µg/kg body weight (b.w.) administered by gavage or in feed, respectively) and the estimated 95th percentile of exposure (0.06 µg/kg b.w.) a margin of exposure in the range of 1000-10000 was calculated. The mouse bioassay has traditionally been used to detect CIs. However, due to poor specificity and ethical concerns it is not considered an appropriate method. The receptor-based fluorescence polarisation method has been developed as alternative, but it needs further development. Liquid chromatography-tandem mass spectrometry methods would be of value for the quantification of CIs, but certified reference standards and reference materials are needed to allow method development and (inter-laboratory) validation.