The Andean lupin (Lupinus mutabilis Sweet) is the only cultivated species of the genus Lupinus originating from South America. Attempts were made to introduce this species to European soil and climatic conditions. The main disadvantages of the Andean lupin include too long and non-uniform maturation of pods in a plant, dropping flowers and pod buds, and a high alkaloid content (up to 5%). The aim of this study was to identify in post-mutagen treated material genotypes with low alkaloid content in seeds, which would be useful for improving L. mutabilis by breeding. The iodine test was annually performed to test the presence of alkaloids in seeds, using Lugol's solution (I in KI). Based on the turbidity of the test samples, the investigated plants were divided into four groups, labelled as follows: G - individuals with a high content of alkaloids (very bitter), P - individuals with an intermediate content of alkaloids (bitter), PS - individuals with a low alkaloid content (fairly sweet) and S - individuals with a very low alkaloid level (sweet). For further propagation, mainly individuals from the S and PS groups were selected, and by part from the group P, while all bitter forms (G group) were rejected. Thirty chosen lines were examined for the content and composition of alkaloids by gas chromatography. The alkaloid content did not exceed 0.1% in 13 favourable lines, and even two lines had less than 0.05%. The seeds of the studied material contained 7 to 9 different alkaloids. The prevailing alkaloids in the seeds of the Andean lupin were 4-hydroxylupanine and lupanine. Significant progress has been achieved in reducing the content of alkaloids in subsequent generations of the investigated representatives of Lupinus mutabilis from South America.