French language Q&A Forum

If you say the stem has to be the stem of the infinitive, then yes, you'll find lots of irregular verbs. But there's a much better rule, and I'd say the few verbs that don't follow it could be called irregular in the Subjonctif Présent.

- je/tu/il/elle/on/ils/elles: the stem is the Indicatif Présent third person plural, minus -ent

- nous/vous: the stem is the Indicatif Présent second/third first plural, minus -ons 

Examples:

aimer -> ils aiment -> aim-

venir -> ils viennent -> vienn-

tenir -> ils tiennent -> tienn-

prendre -> ils prennent -> prenn-

...

There are not that many exceptions to this rule. Some important ones:

NOTE: where there are two stems, the second one is for nous/vous, the first one is for all others.