Despite the crucial significance of sexual satisfaction in marital relationships, this phenomenon is under-investigated. Scales or subscales of sexual satisfaction used in research and psychotherapeutic practice are primarily based on disorders of sexual relationships. The aim of this work is to develop a new scale of sexual satisfaction based on the concept of a healthy long-life relationship. In contrast to previous clinical and sexology scales and subscales, this scale is aimed not at the assessment of sexual disorders, but at the assessment of fully -fledged sexual marital relationships. After the verification of 126 statements describing sexual relationships derived from vocabularies and other scales, 16 positive statements were selected and modified. They were accompanied by a frequency “never – ever” frequency scale. The fFirst studies using this scale have shown its good construct validity and high internal reliability. FISS has strong positive correlations with “Love” subscales (“Intimacy” – 0.75, “Passion” – 0.73, “Commitment” – 0.69) and a weaker correlation with the “Jealousy” scale (0.45). Cronbach’s alpha for women is 0.928, for men – 0.943. The scale ensures the assessment of sexual satisfaction in long-term partnership relationships. The nNext stage of the FISS development should involve factor analysis and comparison of groups with different marital status.