The present progressive tense is formed with the auxiliary verb estar plus a main verb in its present participle form (e.g. estoy escribiendo). The present participle is formed with the stem of the verb plus -ando (for -ar verbs) or -iendo (for -er and -ir verbs). For example:

hablar -> hablando (example sentences)
comer -> comiendo (example sentences)
beber -> bebiendo (example sentences)
vivir -> viviendo (example sentences)

In the case of -ir stem changing verbs the stem vowel changes. For example:

preferir -> prefiriendo

pedir -> pidiendo

venir -> viniendo

Verbs with stems that end in a vowel also have an irregular form:

caer -> cayendo (example sentences)
oír -> oyendo (example sentences)
traer -> trayendo (example sentences)

The verb estar must be conjugated to match the subject pronoun. For example:

Just like English, Spanish uses the present progressive tense to describe actions that are occurring while one is speaking (e.g. John is writing a letter). Also similar to English, the present tense is used to describe actions that one does repeatedly or habitually (e.g. John writes a letter every morning). One difference between the two languages, however, is that in Spanish the present tense can also be used to describe progressive actions. For example:

• ¿Qué haces? / ¿Qué estás haciendo?
  What are you doing?
• ¿Qué escuchas/ ¿Qué estás escuchando?
  What are you listening to?

Progressive tenses: estar + gerund.

To form a progressive tense, use the appropriate tense of the verb estar immediately in front of the gerund, e.g.:

• No me molestes; estoy trabajando.
  Don't bother me; I'm working.
• Estábamos almorzando cuando llegaron.
  We were eating lunch when they arrived.
• Estuvimos haciendo ejercicio por tres horas.
  We were exercising three hours [Or: We spent three hours exercising.]
• Dudo que estén practicando a esta hora.
  I doubt they're practicing at this hour.

Note that any tense can be used to form a progressive, even the preterit as given in the third example above [note that there the action is viewed as having been limited to a three hour period]. However, the present and imperfect tenses the ones most frequently seen.

Caution: As the name indicates, the progressive tenses express an action viewed as being in progress. Do not use the progressive for other purposes, such as for expressing a future action: “We're leaving for Mexico tomorrow” (Salimos para México mañana [NOT Estamos saliendo).