This is a study of tense variation in "si"-clauses in Buenos Aires Spanish which basically consists of the substitution of the conditional for the imperfect subjunctive. The highest frequency of imperfect subjunctive shows up in +Contrary examples, while the conditional substitutes much more often in -Contrary examples. When the conditional replaces the imperfect subjunctive in +Contrary examples, the variation relates to other linguistic facts. Two examples of these are examined: (a) when the "si"-clause is negated, and (b) when the verb is the second of two conjoined verbs. The analysis shows that the use of the imperfect subjunctive in negated "si"-clauses involves a decodification process which conflicts with the routines for negation in Spanish, and that the second position for a verb in a "si"-clause is an environment where the difference between protasis and apodosis (and therefore between condition and consequence) is sometimes neutralized. That is, both factors are shown to constitute linguistic environments for which the conditional is better suited than the imperfect subjunctive to express what the speaker means, and to guarantee a more accurate reception by the hearer. (Author/CLK)