The period after the fifth congress (21–24 May 1975) witnessed a boost in the popularity of DİSK, which now counted 25 members. The most important growth occurred with the affiliation of the former Türk-İş member Genel-İş under the leadership of Abdullah Baştürk. By this time the membership of DİSK was close to 600,000. In 1977 participation to the First of May demonstration organized by DİSK was even larger than the previous year, but the peaceful demonstration ended in a blood bath when unknown persons opened fire to the crowd toward the end of the rally and 35 people were killed.