The results are given of a detailed spectrophotometric investigation of NGC 3353 based on observations with the 6-m telescope of the Special Astrophysical Observatory of the USSR Academy of Sciences with reciprocal dispersion about 65 A/mm. Four separate condensations, the brightest of which is identified with the object Mark. 35 are investigated. The spectrum of Mark. 35 contains emission lines of the Balmer series from H..cap alpha.. to H/sub 12/, He I lambda lambda 7065, 6678, 5876, 4822, 4472, 3820, and the forbidden lines (O I) lambda lambda 6350, 6364, (O II) lambda 3727, (O III) lambda 5007, 4959, 4363, (Ne III) lambda 3869, (N II) 6584/48, (S II) lambda 6717/31, (S III) lambda 6310, (ArIII) lambda 7136. In another central condensation, in the presumed ''nucleus'' of the galaxy, the emission lines are weaker, and, beginning with the line H /sub 1b/, absorption components appear, these becoming stronger in the later members of the series. In the ''nucleus,'' there are fairly strong forbidden lines: (Ne III), (O III), (O II), (S II), (N II). The relative intensities and equivalent widths of the emission lines are calculated, and also the chemical composition in Mark. 35 and in the ''nucleus.'' In theirmore » physical parameters, both condensations are similar to super associations (giant H II regions). It is concluded that the excitation sources of the condensations in NGC 3353 are stars of early spectral classes. NGC 3353 is most probably a nest of super associations.« less