The purpose of the study was to explore relationship between the menstrual cycle and suicidal attempts. A study was performed on 151 fertile females who were admitted to the Clinic of Internal Diseases and Acute Poisonings Medical University of Gdańsk during the years 2002-2003 because of suicidal attempts. The inclusion criteria were as follows: fertility, regular menstrual cycle, lack of oral contraceptives, willingness to attend the follow up and willingness to see a psychiatrist. Using the anamnesis the patients were also grouped according to the menstrual cycle into menstrual, follicular, midcycle and luteal phase. According to psychiatric investigations every female was classified to the respective category: situational reaction, depression, schizophrenia, alcohol addiction and sociopathy. Severity of intoxication was classified according to Poisoning Severity Score (PSS). Statistical analysis was done with the use of chi-square test with Pearson correction. Suicidal attempts were the most frequent among females during menstrual phase. The most common diagnosis in females who have attempted suicide were situational reactions which dominated in patients aged 14-21 years. Among attempters with the psychiatric diagnosis of depression, schizophrenia and alcohol addiction the degree of poisoning was significantly more severe than in the patients with situational reaction.