日本語道場 — Nihongo Dojo

～最中に

~saichuu ni

right in the middle of

When to use it

Use ～最中に to pin an event to the exact moment another action is at its peak — typically an interruption, disturbance, or badly timed occurrence. Unlike ～ている間に (any point during a span) or ～ところに (the instant something begins), 最中 stresses that the activity was fully underway, which is why the second clause is so often unwelcome. In business writing it appears in incident reports, apologies, and explanations of why something went wrong.

Formation

Verbs: 〜ている + 最中に (progressive form required) — 説明している最中に. Past-tense 〜ていた最中に is possible when the whole scene is framed in the past.
Nouns: noun + の + 最中に — 会議の最中に、交渉の最中に. Works best with nouns denoting an activity or event (会議・作業・食事・決算).
い-adjectives / な-adjectives: not used. 最中 is a noun meaning "height/peak of an activity," so it needs an event, not a state.
Variants: 〜最中 (no に) when it ends the clause as a predicate — 今、調整の最中です; 〜最中で also occurs. Emphatic 真っ最中 is common in speech.

Examples

My phone went off right in the middle of the meeting.
Leaving your seat mid-negotiation is rude.
An audit request came in while we were in the thick of closing the books.
I was cut off right in the middle of my explanation.
We are in the middle of investigating the cause.